Great info- Thanks!
2 questions about it:

First, based on mot29 said, the itinerary with IAH I gues I could book through NWA or whatever-- But would that type of itinerary work for a pre-set (with its own rules) Y fare (which is setup for volunteers... therefore I have to place it via the phone and whatever the rep is able to do). It seems that they wouldn't let me do a DTW-IAH-DTW in the middle of there flight (which has a set price, thus i don't think I can just add in legs for a little extra). If the answer is NO-- do you think AVL-DTW-IAH-SFO-NRT might workk? And also, I probably couldn't just stick AUS in there instead of IAH, right?

2) I didn't really understand the : " Yes, you can take advantage of the free domestic upgrades, but only where you have a change of flight number; watch out for the infamous 'direct flight with change of gauge' as they'll use that as an excuse not to upgrade you on the domestic segment."
Is it saying as long as my AVL-DTW on pinnacle is a different flight number than my DTW-IAH or whatever flight, then I will get upgraded?

Thanks