I assume by "engine oil pan" you mean the drain plug?

I believe it's either a 18 or 19mm socket that fits. Be sure to have the socket squarely over the bolt head. Remember "lefty Lucy" "righty tighty." Wear some Mechanix gloves or something to keep you from hurting your hands. If at first it doesn't bust loose, try tapping on the wrench just ever so slightly to help motivate it loose.

The plug shouldn't be in super tight. It's not a tough job to get done.