904 advice needed

I would do it myself and get the parts from somewhere like bulkpart.com or hughes. You can get a basic rebuild kit or build it up a bit more for any future add-ons with things like Red alto clutches, kolene steels, Trans-go shift kit, etc. Get a good service manual like the atsg one. I also got the dvd from Paul Zank that goes through a complete rebuild start to finish. Its really easy to rebuild these transmissions. Plus you will save yourself a few hundred bucks and have some new found skills to boot.