Not really that complicated just A LOT of reading on what every teeny tiny little parameter does. The GM side of things is pretty well explored and explained, Ford still has some theories about its load calculations and how the computer "makes" it's power (at least from what I've read) but is still pretty known.
Yes, HPT does have a tune repository so you can look at other people's tunes that they have uploaded to get an idea of what you need to do or why you can't figure something out. Great example is my vette kept dying immediately on clutch in trying to coast with the AC on. Found someone with a similar big lopey cam and was able to smooth that out by using some of their idle air/spark tables (of course, I used it as a baseline and was able to dial it in for my specific car).