There's neutral support, but since the gaps in the fields are huge (a couple of hours between the leaders and stragglers), the support gets spread pretty thin. I rode my tubulars last year, but my teamate had his family driving support for the 2 of us. Next year a different teamate and myself are hoping to bring someone along to drive support for us, I don't think I'd ride the tubulars without knowing that a spare wheel was only a couple of minutes away, it's also nice to get bottles of my own drinks, instead of HEED. Most of the riders and volunteers at this race are friendly and willing to help (quite a contrast to the local racing scene), I'd see if you can make arrangements with one of the support vehicles, to carry your extra wheels.

As far as gearing goes, I would strongly recommend using a compact. I know people that have done this with 38x27 gearing, and they didn't make it the start line the second day. On the first day the last climb has an extended section (~2 miles) at an average of about 10%, and the last mile or so of the race has a very nasty stairstep section in the 15-17% range, I can barely push 34x27 up that section at the end of the day. The last 3 miles of the second day are switchbacks that have an average grade of ~10%, not to mention the miles of very steep rollers at the start of the last climb. I could tackle any of these climbs on their own with a 39 up front, but when you hit these after riding 80 miles and 13,000', they become monsters. This is the only ride/race of the year that I use my compact, I put it on about two weeks before race day, to make sure that it's dialed in, and it comes off the week after the race. If you can mash gears endlessly, and not destroy your knees, than go for the 38.