I've been doing mine for years, ever since I lost gears at the track and a racer helped me fix it whilst there. We got away with just band adjustments at the time but I bought a few books, trawled the 'net and re-built my first one soon after. I made a slide "hammer" to pull the pump housing and a couple of spring compressors for the drums. I had various bits of pipe turned down to use as bearing drifts. I don't have a stand, they go on the bench supported by wooden V blocks, but this makes fitting the drums onto the o/p shaft awkward, easier to do this vertically. I'll get round to sorting something for that one day but so far I've managed.
My approach to rebuilding is modular, I just do the pieces that come out in one lump, ( V/B, pump, front drum, case, etc). Do them one at a time, clean, check, measure, repair and replace (if needed), then set aside ready for refit. Use a good auto box assembly grease and a lip seal installer, take your time, soak the bands and clutches, measure everything and write it down. Air check. So far I've done OK, I did burn up a front clutch pack a couple of seasons after a rebuild but I didn't replace the front pack as they were still within spec (albeit on the loose side). Lesson learned . I have been asked to build 'box's for other's but it's not something I want to get into, I usually encourage them to do there own.
I usually refresh a box after 4 seasons but we don't race as much here, as you guys do over the water. 6 or 7 meetings a year if I don't bust stuff from wheelstands, which I have done for 4 years running now . I get my parts from various vendors, CRT, Marsh performance, A&A etc. H/D Bands and racing clutches (Alto Kolene) are readily available over here, or they at least used to be. I have a good selection of spares.
HTH's