The good news? We put our lowers together yesterday. It took about 2.5 hours with a 45 minute break to find the front takedown detent on the man's rifle, since he lost control of it and it took off. They aren't kidding when they say to be careful! At any rate, the rogue part was found and installed (using bent-tip needlenose pliers, instead of the tool he bought). To those building their own: take your time. We didn't rush, and that was the only issue either of us had.
the before shot, with all parts laid out:

the after shot:

The other bad news? My 1911 plans have been derailed. Apparently Para DOES NOT ship their GI Expert with the spent casing, per MD law, so I can't get it. This, coupled with other bad news on Saturday (my eldest, and first EVER, pet died. RIP Delirium, you sweet little scaly kid), basically guaranteed I had a cruddy day.
Thanks, Para. Thanks a lot. Looks like either S&W or Springfield will be getting my business henceforth.