A couple other things I have learn to check are testing the windshield seals with my thumb nail to see if they are hard and soon to be replaced, and also taking off the oil cap and checking the first lobe of the cam.

The first cam is close enough that you can feel for a flat spot, or see if the cam is scored. Mercedes changed the cam from ductile iron to white iron about 1980, and I have come across a couple of engines with the ductile cam scored, and a couple of white iron cams with flat spots on the lobes.

I've also learned to open the sun roof and check to see if inside the opening is rusty.

W.