I changed the clutch on my 05 CTSV and noticed a coating of oil on the bell housing and the side of the trans that faces the bell housing. It looked like the rear main seal was leaking.

Now that I have everything back together, the starter will not crank. I turn the key to the start position with my foot on the clutch pedal, and the car acts like I don't have the clutch pedal depressed.

Could the engine oil from the leaky rear main seal ruin the starter? Or do I need to look at the clutch pedal position switch?

 

The chance that it was leaking for a period of time and then choose not to work once you fixed the leak is slim. Do a volt test at the starter or pull the starter off and bench test it.

 

I've seen starters come off of old motors, like 69s ones with with 2-pc rear main seal, that looked like they had been bathed in it for 100,000 miles, and worked fine up until they wore out.

Nothing to worry about.

Check for 12V at the solenoid, and if it's not there (probably not), track your way back through. Clutch pedal switch is a very likely candidate.