Best deal on a 904?

It's like a light bulb, I know what it does but I can't explain how it does it. It's why I like a professional to build my transmissions if it's for a special duty. Transmissions don't interest me enough to learn it, and I don't need it enough to justify it.
If it's just a matter of the valve body it's just 10 bolts that hold the valve body in..
Why people let something as simple as an automatic transmission continue to be a mystery is far beyond me.. I'll never pay somebody thousands of dollars to put $120 rebuild kit in my transmission...
I'm shocked you haven't covered this on you boob but then again something useful like teaching people how to use a $99 Harbor Freight flex wire welder would be extremely useful as well...