If you take your time to investigate and learn about the car and systems along with reading and searching here I believe that you can solve many of the problems yourself. Your costs will be similiar to those recent experiences and much more satisfying. This Mercedes is an amazing car, I bought mine on a lark and intended to sell it promptly. However, the more I drive it, the more I really enjoy it. It is very well engineered and solid.
Tackle your problems one at a time and do a search to fine tune questions for the forum.
I believe everyone really is here to help.