Sound like your ready to load after installing the barrel. I use my Lee 223 Rem collet die on my 223AI and it works great. Don't worry about case lengths when you fire form as the cases will shorten when blown out to AI dimensions. You may want to look at a body bump die when chambering gets a bit tight from collet neck sizing.

In my experience, Winchester brass is better quality overall than RP so I recommend fire forming with them. If at all possible, use new or once fired brass for the forming process.

If I'm leaving anything out, someone please correct me...........getting old is a b-tch.