One thing I found out over the years is that many and I mean even techs can watch and learn how to disassemble and reassemble transmissions and do it pretty good. But many never did learn just how they work and how to diagnose a problem as in my eyes thats the harder part and what makes a good trans person and thats understanding just how they actually work and it makes it so you can diagnose trans problems without having to follow a book.
But what you want to do I have seen alot of guys do as the 727 is not to hard to learn how to mechanically take apart and put back together. Its nice help if you have a friend or someone with you thats done one before just in case you need a little help. Its always nice to have someone around who has done one at least once before. I agree with some on here that you may want to just have a trans shop go through the O/D unit. I had access to the special tools like the alignment shaft which I did not take out until I was ready to install the O/D unit and the tool and press to compress the large spring for the direct clutches. There is also a few special tools for measuring what size shims go in the overdrive unit as many just use over whats in it and get away with it but if you change any hard parts in the O/D it can change what size shims it needs. Good luck with it and remember there is plenty of people on here who will help you if you have any problems. Thats the nice thing about Moparts and that is that most on here are always willing to help a fellow car person. Ron