You're going to have to look at it, most all of them had a lift cylinder with 4 shafts. Most any repair service is going to want to pull the whole cylinder out and rebuild it. It is possible to just replace one seal if it only has one leaking, without taking it out of the forklift, if you can find someone to do that. I would guess $1000 for a complete rebuild. A pneumatic forklift like that, that can start up and be used maybe worth $1000-1500 ??