904 interchange question

I was looking for a plug and pray solution to my slipping transmission. Can't find a 904 with less than 100k miles on it around here yet. If I'm going to be tearing one apart I'll just tear into my current one. I had coolant leak into the trans cooler about 8 months ago so I knew this day was coming. I always wanted rebuild/understand an automatic transmission. I've looked at manuals and videos, it looks like something I can tackle. Researching kits now.