what's wrong with your entry-level bike now? Are you having problem with braking performance? (probably not) are you having trouble with your fork? (seems more likely) Are your shifters and derailers working properly? If not, an upgrade could be nice. If they're alright, i'd just give 'em a fresh chain and a tune-up.

if you want a better bike, there's many avenues to take. I personally seem to put a higher priority on good components than on a nice frame, but i'm pretty sure i'm in the minority on that one. If you're just starting out riding trails, you might want to keep your trek as-is while you get a better feel for your own preferences.

hth
-rob