I've broken 3:00 several times, in my late 20s, off as little as 40 miles a week. I was running about 16:30s at the time, without training for it specifically.
I didn't run in college, but I think I have some talent that makes 3:00 a fairly easy bar--and I never had your talent (my PR is about 16:00). That said, if you can handle a couple 20+ milers in training, you'd be fine. You might screw up your first shot, since that's fairly common with talented guys new to the marathon who want to test their legs a bit.
My advice for the run is to go out around 3:00 pace for the first 15-18 miles (only a bit under 7:00, right?), then pick it up. That still gives you lots of distance to pick up the pace and run well under 3:00--because lets be honest, you don't want to run 2:59. You'd prefer to break 2:50 just to show those laymen!