do a search and you will find the answers.
no, the power steering does not share the transmission fluid...it IS filled with Dextron III fluid though, as is the T-case and Tranny.
Same fluid, different fluid reservoirs.
Tranny has a fill hole on up top and drain hole down bottom. I believe Isuzu wanted $300 from me for servicing the tranny which only included a drain/fill and changing out filter.
when they power flush they hook up a pressurized machine and use about 3 or 4 extra quarts of fluid to flush out old fluid.