I do not know if you do any mechanical work. I tend to do my own.

I would at least try to establish what the problem is. Broken camshaft or whatever. Some situations will be nasty and some not so much. It just depends. I would at least pull the valve pan or pans. I kind of doubt that a main or rod bearing has locked the engine up at that millage.

Also you might try asking Mercedes what is the typical failure issue with these engines. At low overall millage. They have to know as there are other members reporting knowledge of the issue.

Timing chain issue? At the potential dollars otherwise is concerning. Two reports that engine is locked up are not really that informative. Sometimes a broken cam is really bad and other times not that much.

Personally I would not write that engine off until I knew a lot more.