Are you sure? I've heard the exact opposite. I heard that they won't install a thumb safety because it changes the info that the ATF has on the pistol model number. Sounds dumb, I know, but I've heard it from more than one source.
When I researched doing it, at the time the way to do it was to...
If you are new to pistols, you could be limp wristing it. The best way to load a full magazine is to lock the slide back, insert the full magazine, and then left the slide go with full force, don't "ride" it down or it might not go into battery. Have an experienced shooter handle it and see if...
6 - CMC 8 round 1911 Stainless Power Mags, new in package. $140 shipped.
Also a pair of VZ Grips, Operator II Black Cherry Magwell. New, Unused. $50 shipped.
Thanks for looking