CMMG makes excellent products. I don't think that you could find a person dissapointed with them.
$1000 with extras may not be too bad, depending on what extras are included.
As far as fit-up between the lower and upper, I wouldn't be too concerned. My bushy isn't super tight, and it still shoots 1/2 moa with handloads. There are products you can buy to tighten up the fit, for fairly cheap.
I would take a look at how many rounds have been run through. I would also add up all the extras and take that into consideration. Also, what model are you looking at?
Chrome Line & Non-Chrome Lined: Chrome lined barrels will last longer, but they don't have the accuracy that a non-chrome lined barrel does.
Mags: You can pick up mags from Midway when they have their sales. I picked up some 20's for about $15 a piece.
I would look at the round count and the extras that come with it before I gave $1000. If it comes with railed forearm and optics (EoTech, ACOG, or Aimpoint would be awesome
) and has 1000 rounds or so, I would jump on it in a heartbeat. Otherwise, it's your money.