I'm not aware of any significant track support for trucks any more - they pretty much died off for racing once truggies came out. There's always the Herts track where you can take it on non-race days, just to play around with.
http://hertsnitromodelclub.co.uk/
I wouldn't bother changing parts unless you wear out the originals - if you get into racing you'll end up buying something else anyway, so save your cash. If you do buy stuff for the Savage, check you're not buying cheese parts (Dragon racing etc) - Innovative RC does a good line in Savage parts.