Any Mercedes that runs out of warrantee can be put on extended coverage from after market co's. This has been discussed before.
All your Mercedes dealers need to do is verify the odomotor has less than 50 thousand mi. Then here in CT I'll be in the same boat soon, I can get full coverage for 3 yrs. up to 75 or 100 K for about $1500-2000. With $100 deductible per occurance or service. No duplicate deductible charges if you have to go back for the same problem. Just save up small problems that need to be fixed and do them at the same time and you only pay $100. Check with different dealers, you'll get different rates. You can also check out
autobytell.com they sell after market insurance.