I'll second Benzmac's recommendation. He found one of only approx 600 500E's just the way I wanted it. (colors, condition, etc) in less than a month and even made pricepoint. He is accomidating, fair, and quite patient. (just ask about the horror stories of selling the 400E!) If you want to custom order a pre-owned car he is hard to beat.
Oh, BTW W140 evaporator cores have been known to be problematic. Its a 4-figure fix...
Hope this helps...Lee