Can a newbie restore a 727 or 904 transmission ?

You bet. Don't need that many special tools. "What books" did you buy, and go over to MyMopar and download 1 or more factory service manuals "free"

The Munroe book,
https://www.booksamillion.com/p/Torqueflite-Transmission-Handbook/Carl-Munroe/9781557883995
and I'm ebarassed...the excellent recent book by a member here

Here we go..........by Tom Hand

https://www.amazon.com/dp/1613253354/?tag=fabo03-20

There are some great videos on the internet

https://www.youtube.com/user/Autotransmissions/videos
Do any of the books list parts for high horsepower applications ?