Can you convert a older sream loco to dcc? And where can you find the decoder.
It can be done, assuming there's room in your locomotive to hide the decoder and route the wiring.
Bachmann sells decoders in their web store.
http://shop.bachmanntrains.com/index.php?main_page=index&cPath=264_274&page=1&sort=3a
You can install DCC is most any loco, but with older models it can be a bit complicated. For starters, you need to make sure that the motor is electrically isolated. You will have to solder the various wires from the decoder into the loco's motor circuit, and headlight if equipped. If you want sound, that will mean having to install a speaker in the tender with additional wiring between the loco and tender. In that case you will want to install mini connectors so you can separate the loco and tender for maintenance. Most decoders today will likely fit somewhere inside the body or the cab of the loco. If there is no room, then it needs to go in the tender.