I gotta agree with rubberneck!
You guys crack me up. The guy asks a few simple questions and all you do is get on here to tell him he shouldn't do it himself. How do you know what his mechanical abilities are?? You guys talk about these "professional" (i use that term lightly) trans builders like they are gods. I agree that the magic is in the valve body, and their time and R&D is what pays off. But if the guy is buying the parts from a supplier along with that suppliers valve body, they should be able to tell him how to set it up to work with their parts. (clearances pressures etc) If you buy all the parts from a supplier they should provide you with the hints and tips they use when building to make sure that you your unit works successfully. If not buy your parts from somebody who will. Trannys are just mechanical pieces. If you are competent, buy good parts and pay attention to what the heck you are doing, there is no reason that a mechanical person can not rebuild it properly.
There ain't no magic there! Buy the books and tapes, make sure you have ALL the right tools and measuring devices, pressure testing gauges, etc. , kiss any warrant bye-bye, take a deep breath, and make sure you realize it might take twice as long as you planned. Then roll up your sleeves, use all safety precautions, and have at it.
Having done more than one, in cars admittedly, I can say from experience, they aren't just 'bolt it together'. The truck units are just beefier. Lots beefier. And a lot heavier. So rent a quality trans jack for the r-n-r part.
The separator plate is critical, along with the whole valve body. Gather all the information you can get your hands on before you turn the first bolt. Talk to people everywhere you find them, even those you disagree with. They all have a nugget of information you can take away from the conversation.
And don't worry if you do something 'dumb' or 'wrong'... the guys here will tell you about it... LOL...
Sometimes it's worth it to DIY... sometimes it's not... But, don't let someone tell you that just because they don't have the heart or tools or ability to do it, that you can't or shouldn't.
JMHO
DaveOo.