There is a mechanism of a rod and latch inside the hatch's locking mechanism. If the problem is that when you press the button on the outside, it moves but doesn't undo the latch, it is likely that part of the lock mechanism on the inside of the door just slipped off the track, as it were. You should still be able to open the door from inside the cargo area if this is the case. Once the door is open (or even if you can't open it) you can pull off the inner cloth/hardboard liner on the door, as it is just a bunch of snap clips that come right off. The inner door handle and its plastic surround should require removing only two screws, then you take out the handle and take the hardboard cover off the inside of the door. Take a look inside the door over to the passenger side. There should be a rod going into the locking mechanism, and you should be able to see if anything is hanging loose in there. A few parts in there can fall off without actually being broken, and you just need to reattach them. It takes some thinking and fiddling, but you'll be able to slip em back together. Hopefully this is the case and nothing else is wrong. I've had to deal with this twice in my wagon and it worked out fine. Good luck.
--
Isaac Babcock - '83 245DL 'Borkie' and '83 244 turbo project