Definitely the synchros, I have the 2nd gear, slider and synchros from my trans rebuild a few months ago sitting on my desk right in front of me.
You might be able to buy the parts and have someone do the work, but most mechanics won't do that unless they're working on the side. If they do they probably won't give you a warranty on it. Unless you know a trans guy you might be better off buying a rebuilt and either swapping your old one as a core, or selling it as one.
FYI it's a hell of a lot easier to swap a tranny than it is to rebuild one. After you drop the h, all you have to do is pull eight bolts, 4 on the D/S and four that hold the trans to the bellhousing, one bolt for the speedo gear and pull the cross member. I pulled my T5 3 times last summer
, the trans is easy, the clutch can be a pita. I'd highly recommend going with a 3550 or TKO if you can find a deal or you can afford it. Just my .02