Updated April 12, 2009
The Prelube additive is for new/rebuilt engine for the first time it runs.
As for changing oil. It does appear that the oil is synthetic. It was definitely different in feel than normal/regular oil. It had a silk feel to it. I did use Mobil Synthetic 5W-30 to refill the engine.
As for the changing the oil, you will need two different sockets. The slid plates are held on by 1/2 bolts. Both plates need remove. The drain plug is a 13mm plug and very easy to get to for removal. The Oil filter is a different story. The filter is very close to the frame and hard to get a filter cap onto it. I had enough room to remove it, but trying to tighten the new filter was difficult. BTW, the AC Delco filter is a PF-61. It may be possible to jack-up the frame to provide more room, however it was too late for myself.
All in all, this is a heavy/solid SUV. The main reason I change my own oil is to inspect and get a feel for the wear/tear on the mechanical parts.