It can be very expensive to own these cars (actually any old car) if you can't do your own work.
You can save a lot of money by removing and replacing the transmission yourself. You could look for a complete used transmission through somewhere like car-part.com - I found dozens of these transmissions within driving distance.
Did your mechanic suggest that he install a used transmission?
1) '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps. 2) '82 J20 360/T18/NP208/3.73, KOs, 7600 GVWR 3) '75 CJ-6, 304/T15, PS, BFG KM2s, soft top 4) '95 VW Golf Sport 2000cc 2D