I picked up a stainless P-13 a couple of gunshows ago for $450. Wasn't really looking for one, but this was too good to pass up. It looks like it hasn't been fired. Shot about 100 rounds through it so far and, once the mag springs were replaced it ran 100%.
I don't think I'd go for the one you describe. For one, I don't like 1911s with aluminum frames. He's selling about $300 worth of mags with the gun. If the mags are factory Paras and not aftermarket AND the gun is in pristine condition, you will probably be able to get your money back out of it if you decide you don't like it. Now I said I wouldn't, but this is you. If you like the gun and you feel the condition is good for the money, then get it. It's not a great deal, but you're not getting shafted either (this is principally dependent upon the mags being genuine Para mags).