I would do the timing chain for peace of mind. I would usually do mine between 200,000 kilometers and 250,000. It's pretty easy on the M102, and don't forget the tensioner. Chain rails are a non-issue on the M102, so just swap the chain and the tensioner.
One of my 2.3L engines had a lifter going south, and it lasted YEARS before something was finally done about it.
1998 C230 "Black Betty"