its probably not your tranny. Can you give a more accurate description of the problem?

If the problem suddenly occured chances are its the clutch. A number of things could have happened such as one of the buffer springs coming loose and getting stuck inbetween the pressure plate and the clutch, the pressure plate breaking (not likely).

Try rev matching your downshifts from now on, if it gets really bad you can still shift without using the clutch but you have to shift slowly and know how to rev match well.

If you are not going to do the work on it they have to drop the clutch ANYWAY to take a look at the tranny....so may as well look at the clutch as the problem. If the tranny is bad just replace it. Its probably not the tranny.