Overfilling your oil can cause seepage in various places over an extended period of time. You might experience blow-by through your oil fill spout or even your oil dip stick. I would think that it might affect engine temps all over.. I would always recommend filling it to factory specs otherwise you might encounter a messy engine compartment.

I can't answer your question due to cause of your engine light coming on. I would ASSUME that overfilling would cause your C/E problem if it illuminates after your oil change and nothing else...

I thought about replacing my oil drain plug with a drain cock/ butterfly valve. I don't know if I trust those though. Has anyone here used a drain cock/ butterfly valve for easy oil draining/ replacing???