You've come to the right place. It's not always as easy as Armored Farmer says, but looking at a used one, you want to:
-Check the items on your list, that's a good start.
-Work the action: When pulling the bolt back does it bind? This could indicate a new recoil spring is needed, or unmatched wear in the receiver.
-Does the bolt latch back positively? If it doesn't latch, there are a few possible causes.
-Pull the barrel, and look at the outside of the mag tube; O-ring-Unless it's pristine replace it, and keep it for a back-up. Rings (Or ring if a very new model; It's a two piece, but one slides onto the other. The older separate rings are better.) They can be cleaned up, but should not have pits, or chunks broke off.
Get (bring) a rag and wipe the outside of the mag tube off. inspect the wear. It should be even, and consistent with the seller's story.
If allowed, pull the action bar/sleeve and bolt out. Inspect the locking block for cracks at the rear of the locking wedge.
None of these is a deal buster, but they will need attention/ repair if worn/broken, adjust your offer accordingly.
Some useful notes-
1100 receivers, if they are going to crack, almost always do so along the bolt operating handle cutout, from the end of it on back, and this is usually indicative of overpowered shells, or a very high round count. If it is cracked there, offer for parts value only.
1100 stocks usually don't crack unless the stock bolt is way overtorqued, and hot shells used. The forearms are fiberglass reinforced to prevent cracking like A-5 forearms.
If you find rust, external or internal, adjust price accordingly. If to be a field piece, it's not as critical. If you find pits, you might want to pass.
The bead is a non-issue. If it there, fine. If not, they are easy enough to do. They are also not necessary. The only reason one uses a bead is to check mount of the gun in those clays sport where one mounts the gun before calling for the bird. If the gun fits, even that's not necessary.
When you have the barrel off, check the gas ports; Magnum (3") guns should have one larger gas port, 2 3/4" guns, 2 smaller ports, and the barrel should match the receiver as to type. Magnum barrels on a 2 3/4" receiver may not function with ligther shells.
Perhaps
@Virginian will stop by with much better advice than I .
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