Another lesson learned today. Don't be like me.
Key point as you are reinstalling the diff, put the drive shaft into the receiver of the diff, you can actually start and insert the driveshaft Torx bolts as well. This is probably a
"Everybody Knows that" (Geico type situation), but when I was initially installing the diff, I thought the driveshaft was affecting my ability to position the diff so I moved it out of the way. Once the diff is in (and of course torqued to spec) I just couldn't get the driveshaft to clear the flange on the diff to get inside so I could bolt it down. Big Mistake!
Don't waste your time (like I did) trying to loosen the center bearing mount, after removing the heat shield, it just doesn't help. Just buckle down, swallow your pride, and remove the diff, you just need to lower the diff a couple of inches and the driveshaft will drop right in. It's easier the second time, just think how much additional experience you're getting!