What's the deal with 5th gear pop-out? Why is this happening? :banghead:

your transmission is in need of a rebuild. you can wait but it will only get worse, and 3rd gear will probably be the next to go.

So does this mean that the tranny will start to completely refuse to stay in gear after a while? Will I be able to just hold it in gear????

get some rubber bands.....

when my car started popping out fifth gear i just replaced the ball bearings and it fixed the problem

you mean the output shaft bearings? yeah but i doubt the OP knows how to do that. hes better off replacing the seals and synchros also since its already opened up.