You show a 1983 Mercedes 300cd in your profile.
A turboed Engine should have a working Oil Cooler.
Likely OK for driving around Town till fixed.
Locate a place to get the Part first.
The Oil Filter Housing has to come off to get at the Thermostat. The Stock Block to Housing Gasket is really nicely made.
There should be pics of the Gasket in the below thread.
Fuel Injection Pump Removal with the Oil Filter still on 617.952
Fuel Injection Pump Removal with the Oil Filter still on 617.952