Same thing happened on my 92 ES300.
I purchased a replacement regulator from a wrecker.
Like you, I seriously considered trying it myself, but after consulting the service manual (thanks LOC!) I decided it would likely end in tears.
The Lexus dealer installed the reg from the wrecker for me, good as new!
The way to keep the labour cost down is wait until you are getting something else done (if you can) and remove the door lining / refit youself. That way you are only paying them to actually re-fit the regulator and nothing else.
