96' Vw

Hi, I recently bought a 96' VW Jetta in perfect body/engine condition for $1000. The only thing was that it had/has an automatic transmission problem. The problem first included a minor slip from 1st to 2nd and then a minor slip from 3rd to 4th. Eventually I had no 4th gear at all, and it is currently in that condition. Of course now I am not driving it, and am working on getting it fixed, but obviously I am getting no where fast! I would like to avoid at all costs buying a new/refurbished tranny, and am currently exploring a service bulletin repair kit that involves the selector valves in the transmission. Thank you, and any suggestion will be welcomed!