Looks likes you made out like a bandit, but do let me know of what you think of the 11-87 gas piston and seal ring on the 1100. I did a parts rebuild on my old 1100 (60 K rounds plus) a few years back (didn't need it, but was bored that week end). The one thing that did sour me was the harder recoil from the 11-87 gas set, and ended up putting the old 1100 split piston/seal back in the shotgun to tame the action recoil back down. With your outer mag parked (my 1100 is blued), this may work in your favor due to the added resistance from the park on the tube.
As for the new follower, was the mag tube rusted/pitted and caused excess wear? If so, you may want keep a close eye on the inside of the mag tube during cleaning. Mine had some slight rust (caused some shell sticking feeding problems out of the mag), but it happens when you use the rifle for an oar/goose club, and get stuck in the beyond muddy goose pits for a couple of days without cleaning (read dropping a few shells in the mud and just shoving it into the mag in a hurry as you have a group of birds incoming isn’t great on a shotgun). I ended up just making a steel wool wad on a jig/few cleaning rods and polishing the inside of the tube out to remove the rust.
Note: the shotgun got a couple of lake baths those days to knock off the mud so I could grip the dam thing, so don't just assume that the inner mag tube is going to rust at the first chance it gets.
As for the trigger, might want to stone it up a bit if they did anything to it, and doesn't hurt to adjust the trigger spring a wind or two to get the pull down (mine is set up for a 2.5lb break without creep to match my other shotguns)
I guess that only thing that I really don't care for on my 1100 shotgun is it patterns on the bead, and not above it. I had a chance to pick up a 1100 trap comb butt stock with matching forearm years ago for little over $200 to solve the problem, but figured what the hell since I dam near never shoot it unless I need something to take in less than ideal conditions for the O/U's.
And to add, you know that this thread is meaningless without photos!!!!!!!!!