if the front of your car is light better put some water in to get up the waterfall. better get used to using the front winch to control the suspension on the climb as well or you could be there for awhile. the waterfall WILL be the gatekeepers for the 10-15 that make it in. those that make it will hit the waterfall in 1-2 shots.
the rest of backdoor is techinical but really no big deal. I would imagine they will go all the way to the top with a quick descent down the backside and then through the side of the hill back to the starting line.
I would get out there at least by Tuesday so that you can run backdoor and then on Wednesday prerun some of the KOH course and get back early so you can prep your car for the next day.
Get ready for the pounding that the WHOOPS will put on you and the car. They are no joke.