[Junkbone]

I have been over the topic here in the forums but cant find my particular problem. 88 g50 was shifting fine one day and the next popping out of 5th gear only on decel and in no other gears. While accelerating I can gently pull back on the stick and it feels as it should. It feels stuck, or secure in 5th. The second I let off the gas I can visually see the stick move to the neutral position. I have only glanced at the engine and tranny mounts so far. Still need to get the car on a lift. I guess my question would be, what else to check and in what order? what is the most likely culprit. Syncros? What will that cost me?? Dammit man! Thanks.