Here is another suggestion if you're really attached to the car. Who knows how long the head gasket will last on this one, though.
http://www.peachparts.com/shopforum/showthread.php?t=271136
That would cut your repair bill in half.
Also, I had the head gasket replaced on my first E320 wagon with an independent Mercedes-only specialist for $1200. For my second wagon, I was able to find a used wiring harness that was replaced recently before the car was wrecked for $250.