Read this:
Replacing Chain Guides
And this:
Severe Chain Guide Debris - Oil change
If it was the plastic guides chances are nothing was damaged. Mercedes, particularly the 450SL could rattle all day long for years until the owner finally gets annoyed enough to replace the guides and chain. You can easily test the compression by hand cranking so start with that. If compression is good then really you just need a new guide and maybe tensioner. Hell of a lot cheaper than an unneeded rebuild. In short, do more testing.
If you have an OBDII reader connect it and look for the tons of error codes your car would have thrown out if the engine was self destructing. You don't need to turn the car on to read the codes / only to the Just about to start position.
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