The course isn't too climby. I ride a geared Gary Fisher Superfly and have no problem riding the whole thing 2/5.
2/5 your max speed would be about 7mph. 2/1 is a little better but I like a little more than that. I ran a 36/16 and it was good you might run a hill but the course is mostly flat and you can go in that gear. Good luck and have fun.
I don't ride a single speed so I can not help with gearing but I can describe the course. As others have stated mostly flat with lots of small rollers. There are 2-3 longer climbs that peak around 10-12 percent. There is one hill that hits 25% for a bit.
I have run 61.125 (29er with 34:16) gear inches for a few Iceman's. I was thinking of increasing it, but with 4000 total racers this year it will be difficult to keep momentum and climb.
-edit to correct gear-inch - oops!