I live in Madras which isn't too far from Warm Springs, and I have floated that section many times. There isn't really anything to worry about as far as obstacles go. If you are at all worried, stay to the left of all of the big islands and you will be fine. As far as tribal permits go, I wouldn't bother buying one; I am pretty sure that the side of the river you would need a permit for (West side) closed November 1. Check out this site: www.tribalpermit.com I have heard that the Deschutes flows at about four miles per hour in that section, and it is approx. an eight mile float. It can easily be floated and fished in a day, but with the days getting shorter, you would obviously want to start early to get maximum steelhead time in. If you do decide to buy a permit, they can be purchased on line. If you need to get one in Madras they have them at Bi-Mart and Tiger Mart. One more thing... the Deschutes is a heavily regulated river, so make sure you check the regs before you get here. There are some unique rules to abide by. For instance, anything west of the main channel of the river is considered part of the jurisdiction of the tribes of Warm Springs.
Good luck and catch a big one.