Transmision problems 94 Grand Cherokee 4WD

My transmision would work for about 50 feet then slipp out of gear.I would have to turn the motor off in nutreal for a few minutes start it back up and get to about 3000rpm and barely move another 50 feet and then do it all over again. The trans was running fine that mornig and then that happened, the atf is clean and full, id like to do the repair my self being money is an issue