As far as automatic transmissions go...they are easy and pretty basic. However there is alittle more than "stack and repeat." If you really want to do it...get yourself a transmission manual and read up on it. Better to read through the procedure before getting into it. There are a few special tools required, but you can make do without them for the most part. The one tool you will need is a good (strong) set of snap ring pliars. Also a very clean envrioment to do the work in.
I've done over 10 Th350's, a few Th400's and 2 700R4's. The first Th350 I did, I did when I was 16 (with the help of my uncle)...took us about 2 nights of working on it to get it completly done. Worked perfect once I put it back in the truck. The next one I did wouldn't stay in third gear (turned out it was because I mixed in some Th350c parts), but had a wicked 1-2 shift. The rest I have done have worked great.
Also don't even think about rebuilding the transmission without flushing the cooler/lines and getting a new torque converter.