Ya done good 1BMF.
A greart rifle a a good price.
As for mags, you should be able to pick up some nice ones here on the Equipment Exchange, my wife's prefers the Thermolds and USGIs.
Ammo, there are several vendors here on the site, as well as lots on the net, a little surfing/comparative pricing will get you what you want at a good price.
Ammo selection for your rifle should run towards the mil spec type, ie 55 grn. in the 5.56 (Q3131A)as it is a mil spec rifle.
No break in should be needed since it has a chromed barrel and bolt, it will however "smooth up" the more you shoot it.
Cleaning kits sold in gunshops are good enough, just a reminder though, be sure to clean from the chamber out.
Never from the muzzle.
Once again welcome to the club, what you buying next?[:D]