For everything you mentioned, I wouldn't pay anything over $520. Right now on Gunbroker. you can get a brand new polished stainless CZ75b for $650 delivered to your FFL, no sales tax.
Yeah, I was going to say 500 - 550
No OEM Mags (and there were two) and no Owner's Manual
Now some of the HiPolished DID come with Cocobolo Grips
I remember Cabela's had their stock of CZ 75 HiPolish Stainless come with Cocobolo Grips
But they DID say "CZ" on them
Hell, offer the guy 500 and see what he comes back with
You may be able to pick it up for a good price, since he's been sittin' on it for over a year