I sometimes carry a Colt Gold Cup .45ACP when the weather/appropriate clothing permits.  I would like to perform a few aftermarket modifications (i.e., beavertail grip safety, commander hammer, carry sights, etc.).  In your opinion, can a reasonably mechanically competent person install these and who's products do you recommend (i.e., Wilson Combat, Ed Brown, etc.)?

Yes, and Wilson. Seriously, I am an amateur at best, and I've swapped many 1911 parts out.

The 45 was designed for troops to care for and is fairly simple to work on.Get 2-4 reference books-I like wilson's and Simpson's but there are MANY good ones.
cpermd

The best by far is the Kunhausen manuals, both Vols I and II are great.  Any question you might have on the 1911 is answered in there.

Personally, I would find an enhanced Colt slide, (if series 80) I think that the Gold Cup sights are too sharp and too high and too fragile for carry. Then remove the adjustment screw in the trigger as they have been known to walk, preventing trigger from being pulled at all. (Or at least loctite it) Then make sure it is reliable with hollowpoints. Then do your cosmetic modifications...and test fire, as some parts may "fit" but not "work". I would say stick with brand names as opposed to generic gunshow parts, even to save a buck.  I know, sorry you asked?

I carry my Colt OACP lightweight XS, with a 7 round mag.
The Government is just to darn heavey for me to tote around all day.