Thanks for the information in this thread. I just bought a NEW rear actuator from lexuspartsworld.com for $84 (vs $125 for a USED one from the Bill's place).
I'll be using this procedure next weekend to install it:
http://www.grcwebsite.com/RR Door Actuator.pdf
By the way, the part number for the actuator is 6913030110.
Hope this post helps someone down the road.
_Shawn