1) I hate FLGRs, if it has one, I swap it out.
Springs are a maintenance item. Recoil springs have a life of about 4000 rounds, IIRC. If you hear a ca-CHUCK after the boom, its past time for a new one...
2) I don't bother changing my trigger, unless its too short. Like the flat MSH, a long trigger is part of "fitting" my pistol. Most of the aftermarket triggers have three holes. Personally, I don't care if it has three holes or is solid. I actually kinda like the long plastic triggers found in Colt 1991A1s.
Trigger jobs are far from uncommon in 1911s, and they usually involve replacing the sear and hammer with parts from a reputable manufacture, such as Ed Brown, Les Baer, STI, the list goes on.
Commander style hammers are just more common than spur hammers, which have bitten more than a few people. Spur hammers also wont work with beavertail grip safeties.
3) The extractor is a major part of the 1911, and one that's improperly tuned will lead to failures to feed or failures to extract. All four of my Kimbers have the stock extractors, one has well over 10k rounds through it. The extractor on my Para lasted about two range sessions, my Springer a little more... The second time I tune an extractor, I install and tune a replacement. Normally a Wilson Bulletproof, 1911Tuner thinks highly of the Ed Brown Hardcores, and based on his opinion, I'll likely use one next time I have to replace one.
4) I don't bother changing the slide stop, unless it needs replaced. I've never replaced one. Some folks prefer extended slide stops, but I never found the need.
5) I'm not familiar with adjustable sight options for the GI dovetail. Yost makes (made?) a nice fixed rear sight though.
6) As Dave says in the shotgun forum, buy ammo, use up, repeat (BA/UU/R, for short). More triggertime is always a plus. If you're willing to get a gunsmith involved, a triggerjob and fitted bbl bushing would probably help as well.
I understand what you mean about the simplicity. I got a used springer years ago for about $400 OTD, and before I took it home I swapped out the MSH and trigger (I don't like short triggers or arched MSHs), and installed some rubber Kimber grips. The extractor wouldn't stay tuned so I got another at some point.
I also bought a magwell, beavertail, extended safety, sights, and a few other parts, that I never installed. The more I shot it, the more I liked it as it was. Its the one gun I miss.