Someone more knowledgeable than I will have to elucidate in better detail, but if I'm not mistaken, many contemporary afterMarket decoders have graduated to a 21 pin plug.

There are many decoders available and you'll have to make your choice.  But I would suspect that in your case, a call to Soundtraxx Customer Service would serve you very well with explaining the eight pin plug, which appears to be outmoded technology, in relationship to what's available and what you might need to do to get your new decoder properly into your engine.  I've always had good experience with them and I think you'll come away informed.

https://soundtraxx.com/

On my secondary layout, I am forced to use no.4 switches.  I too am using Kato Unitrak and while I am generally very well pleased with it, my Bachmann consolidations pick at the frog point with the lead driver, resulting in a little hop that is pretty annoying. 

I don't think there's much I can do with that.  I had the same problem with atlas switches in the past, but with the plastic frog, I was able to bend the point very slightly out of the curve. I'm afraid to try that with the metal Unitrack.

Manufacturers will always tell you the bare minimum switch and curve that their engine can get through, but you should always go as wide as you possibly can with those.  Unfortunately, on my little layout down here on the Gulf Coast, spatial constraints have forced me back into virtual toy train territory with those aspects, unable to run my 2-8-2's.

Man, this is way more work than I ever want to get into.🫣🫨😱😮

I've never seen one, but I'll bet this is the dreaded pancake motor that everyone in this forum who has ever encountered one dreads.  I'll leave it at that, I've never seen anyone care for this motor, but I'll let someone else with experience elucidate.

This appears to be a very early version of the Norfolk and Western J, and that's why the on-line exploded diagram doesn't accurately show your engine, it's for a later run.

Of course it's all up to you, but if any of this is the case, I'd be inclined to install a better motor in that engine.  You've disassembled everything and gotten involved with it so much I would believe that you have the aptitude and energy to pursue that path.

It would help to know what you want to get out of your track.

Do you want ease of assembly? What kind of engines and trains do you want to run on it?  What kind of layout space do you have? A table of some dimension? How big?  All of these play into choice of track.

In the railroad world, the fake wood items are "crossties."  Or, in England and other parts of the world, "sleepers."  Although in certain regions of the world where wood is scarce, crossties now are manufactured from concrete.  I've even seen reports of crossties being manufactured from recycled old automobile tires.

Yes, head end cars please.  We are not all modeling present day excursion trains.

Bachmann is still selling steel rail track?

https://en.m.wiktionary.org/wiki/cornfield_meet

https://youtu.be/cVw3wf91oNk?si=s1z4Tpo7_wd9k1UN

WM Decal sets ought to already have the correct font.

I have a feeling you're trying to replace only one digit in a 3 or 4 digit road number.  I've looked into that before with the Frisco decapod. A single digit from a decal set will certainly never match what's there.  If it's not a minor variation in the font, it will be a minor variation in the height of the numeral, both resulting in a very visible mismatch.

If you replace all three, or maybe four, digits in the road number, they will all match.  Think inside that box and you will have success.

I am very old to the DCC world, almost 20 years now,and I stillpay people to install decoders.  Yes it does cost some money, but my life is much more peaceful and I know the engine will run when I put it on the track.

Google is your friend. Bottomless model railroad wiring videos.

I had multiple steam engines years ago with the old DCC/on board sound decoders and CVs three and four were always supported.

EZ command is the DCC equivalent of the old train set transformer of old......  Just enough to run the train, and today, activate a few sound functions.  That's it.  If you want to do more, you have to invest in a more advanced DCC system.

Toy trains take a whipping.   I have a few cars that were rescued from the toy train world, rehabilitated, and put into service on an actual scale model railroad.  One of my friends said they are like dogs that have been let out of the pound.

It probably wouldn't hurt to have a few extra couplers socked away for the future and quite possibly some wheel sets for the cars too since they can get knocked out of the truck.

Yes, you are presently out some coin but if you buy another engine you already have the decoder.  There's no real loss here unless you intend to never ever buy another engine.

I've been model railroading on and off since the 1960s, and I know I have spent a lot more money on the occasional rabbit hole than anyone here most likely.  I'll start a list if you need one.  This is a hobby, not a business, it's not well suited to profit and loss statements.  You just have to roll with it and accept that not everything will turn up roses.  I did a long time ago and I am happier for it.  Every mistake has one way or another been a learning experience.

Try calling the service department. If you present the case to them that you believe the product has been misrepresented and put you into a situation they might possibly take it back and refund you.  Or exchange it for one with the right decoder interface for you.  Over at least 20 years I've never had anything but good interaction with them.

It's not a typo, it's an advancement in technology. The locomotive webpage clearly says 8 pin, and I'll bet that the Digitraxx product certainly says 21 pin.  A critical difference that a newcomer would not be aware of.

21 pin is the world of today and frankly, for something to be offered still using the old wiring components is not a good thing.  You can always say buyer beware, but when the buyer is completely new to the game, they don't know what to look for. 

You're going to have to try to find a decoder that meets the technology in the engine. But keep the Digitraxx one, it will certainly work in the next engine you buy..... if you carefully read the specs.