Old O-ring is in the trash. I have done a few oil changes in my life before, I'm not a virgin when it comes to working on Mercedes, I owned 17 different ones over the last 14 years.

The issue here is something more serious,

If anyone can provide me more information on the valves at the bottom of the oil filter housing, it would be greatly appreciated...

Is it possible to remove or replace them? How do I test them and/or clean them up?

Thanks