The Government Model's a fairly simple weapon - so look it over carefully for dishing in the lettering, crispness to the slide serrations, and overall fit and finish - both on blued weapons and plated - remembering that plating can (and does) mask a lot of sins.
Internally, it's difficult to screw things up, but improperly-polished/beveled feed ramps can be squared away pretty easily, and slide-to-frame fit can be mated up if there's any major discrepancies - and remember - these were built for 230 grain round-nose Ball ammunition, and not the later jacketed hoppowpoint that was to become so popular - thereby necessitating the greater radius on the feed ramp and barrel throat.
The slide should fit the frame snugly without being too tight (unless you're building for target-grade accuracy, then fitting's another matter, entirely) and should operate smoothly.
There are numerous M1911 forums out there - including the Colt Forum - review them.
As to the shop owner - NIB commercial Colts bring serious money, so if he didn't realize that fact before he looked up the serial number...
The fact that he honored his off the top of his head pricing is a good thing for you - again, cherish him.
The UAW would continue to cause QC problems - note the complaints about the Third Generation SAA that you'll see - but by the late '70's, they would produce a workmanlike Government Model.
Enjoy it - and don't 'do' anything before a few hundred rounds have been fired, except to clean it properly.
If you're not overly familiar with the weapon, ask a couple of guys at your range who shoot the National Match Course for pointers.
The Government Model's a somewhat difficult weapon to shoot well - and requires a bit more range time than do some others - but once you figure out the idiocyncracies, and start hitting regularly - it's both fun and quite rewarding to shoot.
Good Luck!
Vaya,
Scouts Out!