Blake,
Sorry I couldn't get back to you on the wiper motor. The manual instructed to check for power and it didn't tell the exact voltage. So my guess, it's the motor. On the Ls400, Here are something stuffs that you need to look for: valve cover gaskets, rear main seal, motor mounts and transmission mount, rear knuckle bushings, lower ball joints, dip stick o-ring, cv boots.....it can get expansive it you bought the wrong car. Good luck with the buy. Let me know if you need any help.
JPI