Toyota Repair: transmission upgrade???, input sensors, wire harnesses

Question
Corolla 99 VE. The transmission needs to be replaced and also the "thing where the PARKING locks the gearbox" (that is the reason why I never had to unlock the P position to get to R, N or DRIVE).  Well... I would like to know if I can buy a used one from year 2002, 01, 00 and fit it on my car. Also, mine(VE) is the only one that features a 3-speed AT non O/D. Now that I have to buy the transmission and also the gearbox, could I installate one 4-speed O/D on.
Thanks a lot for the help and the helpful website.

Answer
The 3 speed non O/D transmission is a hydraulic controlled transmission, the later version 4 speed O/D is computer controlled, changing over would mean changing the onboard computer and wire harnesses at the very least, since the computer also controls the engine there could be compatibility problems with input sensors, just not practical and not worth the expense.