I'm looking at buying a 1990 GT 5 spd. Everything seems in good shape except it grinds sometimes going into 4th gear. Only fourth and the clutch is in good shape. I assume this would mean a blown syncro. How complicated is it to actually do a transmission rebuild/overhaul on a manual tranny... or how expensive is it to (i'm pulling the tranny out myself) have it professionaly rebuilt? thanx.