Toyota Repair: 1998 Rav 4 (5th gear pops out), salvage yard, shift fork

Question
5th gear pops out when I take my foot off of the gas pedal

This just started to happen.  

Answer
This is an indication of a worn 5th gear shift sleeve/shift fork, the options are to either have the transmission removed and disassembled to repair it or to replace it, the most inexpensive way would be to try to find a good used transmission from a salvage yard.