97 Mazda transmission slipping in and out

Ok, a '97 Mazda 626, 2.0L auto, that slips ina and out of any gear. I have read about all the problems with this tranny but need some reliable facts. I read that this might be as simple as a belt that has slipped off cause ford uses a belt for the linkage. The transmission fluid has been changed and is full, checked it the right way, just need to find out the truth about this problem. So I can fix it, trade it in, or just call a salvage yard to come pick it up. I’m tired of always fixing something on this car. Thank you!!