Final update; I did get to see a gunsmith today, who is experienced with the 1911. He told me that the gun is quite loose, from 30 years of use, but nothing is damaged, or in need of attention.
His advice if I wanted to tighten up the groups, was to get a new bushing, and possibly later on, a new barrel. He suggested I buy only from Colt, as that way the gun is "all Colt", and that if I really did want to spend the money to get it to shoot more like a modern gun, to send if off to Colt - but he didn't think this was a good idea.
I called Colt earlier this week, and ordered a new bushing. I also had a nice chat with the tech person. I asked him how much clearance Colt recommends between barrel and bushing, and between bushing and sleeve, and he told me that Colt doesn't publish information like that.
Thank you to everyone who responded here. Thanks to your posts, and my trying to figure out what you meant, I feel a lot more comfortable now about the 1911. I still don't know what *all* the parts do, but I'm way ahead of where I was when I first came here.