Further... most quality restorations cost more than the eventual value of the finished vehicle so if this is new territory for you, tread lightly. Owners who restore cars tend to do so for their own appreciation, not to turn a profit. If the car is worth a million bucks, then sure, $150,000-200,000 may not be a bad investment for the restoration (costs add up quick on older cars with hard-to-locate/impossible-to-find trim pieces). The shop you hope to approach will have a more solid idea of the value hopefully, but keep in mind too that when dealing with high end restorations, you want to use one of the shops who specialize in Mercedes-Benz, otherwise the details may not be 100% correct and your car will not attract the top level buyers.
Either way, this is a very exciting thread and I hope you can buy the car and do something wonderful with it. Please share pics once you are comfortable doing so.