Hello and welcome. Oil pan job means lowering the frame or lifting the engine, you pick. I have not done one but need to. Theres probably a write-up here if you search for it. Or pick up a repair manual such as Chilton's, it will solve many mysteries as you go. Normally most people replace window regulator assemblies as a unit because if the motor runs slow that means both motor and regulator are aging. The slow motors can continue to work a long time, but might just pick a day and die. As far as where to get them... I'm not a web coupon hound so for the best price you'll have to shop. I've not found local parts store pricing to be unreasonable on window regulators but to each his own. Enjoy your low-buck score!