Well, looks like I may not have the luxury of time to take this repair at my own pace. Was coming back from family pictures in the next town over when I lost power and it threw a CEL on the interstate.
Pulled over and plugged in my little bluetooth OBD2 (thankfully I had it in the truck still). Scanend P0700 and P0796, with P0796 being the code of interest. It's for a stuck 4-5-6 solenoid in the OFF position. I cleared the codes, let it sit for a few minutes (transmission temperature had also creeped up to 180F), turned it off, and then started it back up and stayed on the shoulder till the next exit and took surface roads the rest of the way home. I can definitely feel it misbehaving, not shifting smoothly and slipping a bit in every gear.
Soooo... looks like it is rebuild/replacement time!