check this site for a tool called moacks.
http://www.m-guns.com/tools.phpthere are a couple versions that will let you stake your own carrier key. one version doubles as carbon scrapers and gas tube pullers. if a gunsmith charges you more than $10 to stake your carrier key, tell him to pound sand. if nothing else, send it to me and i'll do it.
heres a good BCG
http://www.bravocompanyusa.com/BCM-Bolt-Carrier-Group-MPI-Auto-M16-p/bcm%20bolt%20carrier%20group%20auto%20mp.htm
I like the auto ones, as it adds a little weight without having to buy a serparate heavy buffer.
magpul mags are good, as are brownells mags with magpul antitilt followers. you might want to check that magpul pmags drop free from your weapon before you buy a bunch. i had a problem with a couple metal mags because the parkerizing was so thick, but a touch up with sandpaper fixed that problem.
this is the sling i use on one rifle. love it! little spendy though
http://www.bravocompanyusa.com/Viking-Tactics-Sling-MK2-VTAC-p/viking%20mk2%20sling%20black.htm
but i also have these items for front and back hookups
http://www.bravocompanyusa.com/Midwest-Industries-MCTAR-08-HD-p/mctar-08%20hd.htm
http://www.bravocompanyusa.com/Vltor-Carbine-Enhanced-Modstock-p/vltor%20aeb-mb%20emod-m%20black.htm
this is the sling i use on the entry rifle. not as secure(bangs you in the nuts if you drop it and try to move)but works for short periods like entries
http://www.extremeoutfitters.us/zmsinglepointsling.aspx
http://www.bravocompanyusa.com/Single-Point-Sling-DUAL-Hook-Mount-Rear-p/sling%20mount%20plate%20dual%20hook.htm
you might be able to get off cheaper without sacrificing capabilities by checking out magpul MS2 sling or something from jerms buddy at SOE
sorry for the long-winded response