Welcome! you are in the right place for anything related to your Crossfire. You will find lots of good information here.

As for the mileage, there are several documented here in various threads with as many or more miles than yours, hopefully that will not be an issue for a long time and many more miles to come.

Repair wise, most of the common issues are not that bad from a cost standpoint if you are willing and able to do the repair yourself, or have someone who can help out in that area, and stay away from the dealership. Parts can be costly, but many can be sourced online with Mercedes equivalents at a fraction of the cost of the Chrysler dealership. A good local independent shop that specializes in Mercedes vehicles can be a great asset for the repairs you do not wish to attempt yourself.

post a few specifics on what exactly is going on with the key and I'm sure someone will point you in the right direction to get that sorted out.

Enjoy your Crossfire!