The OM603 is not very different from the M103 as far as pulling the head, skill- and toolwise anyway. There is a specific sequence for loosening and tightening the cam towers in the OM603 and when torquing the OM603 head bolts you'll hear sound like a submarine that's gone too deep.

Even if the head survived the overheating and a professional inspection suggests it's fine you have to wonder about how long it will last.

Sixto
87 300SDL