synchronizer

how hard is it to replace the sync. in the transmission, cuase 1st and 2nd have to be forced a little bit

Depends on your knowledge of the internals of a tranny. Have you ever done something like this before? It's not a simple job for somebody new to tranny repairs like this.

i dont know much about car trannys, is it an expensive job when im already gonna have my clutch out???

Um... Probably. The tranny will need to be opened up and taken apart in order to replace the syncros. Any shop will charge an arm and a leg to do internal work on a tranny if they will do it at all. Some will refer you to a specialty tranny shop.

take it to a pro, if you plan on modding go ahead and get it doubled up and/or hardened.

or just get a used tranny.