Don,
I might suggest you also do a BunBurner 1500. It is 1500 in 36 hours. It is good for two things. First, if you complete the SS1k, it is a piece of cake to do the BB1500. Second, if you find you can't safely complete the SS1k, it is still a goal to complete an Iron Butt ride.
Any way about it, go onto the Iron Butt Association website and read the Archive of Wisdom.
http://www.ironbutt.com/tech/aow.cfm
Have a great time.
RR