I have a N gauge 4-4-0 American Steam locomotive. It came in a small kit. Is it possible to fit a DCC decoder.
???
Probably not within the loco or tender but you can put it in a trailing car that you permanently couple to it.
Kev-
Let us know which 4-4-0 you have (manufacturer and catalog number). There are some very small N-scale decoders which might fit your needs. However, it can be difficult to put DCC in some locos because of the limited space. And sound can be very tough because you also need space for the speaker and its enclosure.
Be sure to check on your manufacturer's web site if it's not a Bachmann loco. The people there are more likely to know about what works and how to do the install. I note that Bachmann's 4-4-0s don't have DCC but that's not absolute proof that you cannot put a decoder in.
-- D