A few quick notes:

* As others have mentioned Tusayan should have some available rooms if nothing is available in the park. My experience as a former resident/worker (Fred Harvey 1991-1992 woot!) is that Maswick or Yavapai lodge are pretty affordable if you can swing in-park accomodations.

* Mule rides are not as easy as they look. Also, they tend to be booked up more than a year in advance. You might be able to swing a ride on standby, but you've gotta get to Bright Angel at oh-my-god-it's-early and pray.

* Williams to GCNP via train is a nice alternative. Packages should be available that get you hotel and train.

* There are absolutely no jeep trails or tours within the National Park boundaries. There might be some in areas outside the park, but you're not really going to see much.

* Havasupai is wonderful but access is dicey. Access is either by foot or horseback (I believe that there's a helicopter charter that operates, but it's gonna be expensive).

* Beginning in March, the Hermit Road (formerly known as the West Rim Road) is closed to private vehicles. Free shuttles are provided by the Park service for access to viewpoints along the Hermit Road as well as Hermit's Rest itself.

* Bring warm clothes and rain gear. Storms can roll in quickly and leave you a frigid soaking mess even when it's not monsoon season.

I think that cover's the basics. :-)