1) Smith makes good quality stuff, but the need for chrome plating has never really been established. The military does bother with chrome-plating barrels, but doesn't do the bolt or carrier. Certainly no accuracy advantage has been demonstrated. For what it's worth, you CAN get a steel upper receiver for the AR-15 if you want one.
2) There are several excellent triggers available for the AR-15. Two great books are The Competitive AR-15 by Glen Zedicker (available through Dillon's catalog) and Black Magic: The Ultra Accurate AR-15 by John Feamster, available through Precision Shooting magazine. They both discuss trigger alternatives. Duncan Long's Paladin Press book, The AR-15/M16 is my favorite basic book.
I've used several. FWIW, my preference would be the Milazzo-Krieger trigger if you want a military-style, two-stage trigger, or the JP Enterprise trigger if you want a standard style trigger. The Brownell's catalog also carries several styles. Unless you're a better gunsmith than me, having an experience AR-15/M16 smith install the trigger is worth a few bucks.
3) Some folks do find the pistol grip reach a little short, although I do fine with my big mits. The Sierra Precision Rifles grip is nice. David Tubb developed a fairly simple adaptor that offsets the pistol grip and might be just what you're looking for. The Dillon catalog lists this.
4) The area where the bolt locking lugs mate with the barrel is tough to reach, but doesn't seem to be very critical. The military has an odd brush with a forward chamber brush with a rear wide brush that scrubs these surfaces. Most any surplus store should have them for a buck each. I use the jointed military rod and just leave one attached for whenever I clean an AR.
The Brownell's catalog, Sinclair's, and lots of other folks carry some other handy devices. I do like the Delrin cleaning guides that slide into the upper receiver and keep your cleaning rod aligned.
5) There are INNUMERABLE goodies for AR's. Lots are junk or useless, but everybody seems to argue about their choices. The two books I mentioned are excellent resources if you're looking for top accuracy.
My favorite fairly useful toy is the C-More red-dot sight system. Their "Colt Scout Sight" attaches to the carry handle and presents the red dot in the same line as the aperture sight system. It provides for very fast target acquistion, but in no way impairs the use of the open sights in case of the inevitable dead battery.
Have fun, and don't trade that rifle!