$299 is a reasonable deal for a Camp 9 in good shape. That would be a SCREAMING deal on a Camp 45, BTW. WRT trying to haggle, why not? You don't have anything to lose and the $$ is better in your pocket, right?
If you want one of these and the rifle is in good shape, go for it. The Marlins are really fun guns, reliable, and accurate. Replace the wimpy factory recoil spring with a 16.5# spring from Wolf, make sure the bolt buffer is in good shape, get some pre-ban S&W 59xx standard cap mags, and have a ball. I love that Camp 45 I bought in May.