rear seal damage?

I recently had my oil changed and noticed a leak soon after the work was performed. Looking under the truck it seems to be coming from between the tranny and engine. Thinking I would be short on oil, I checked my dipstick and
it was just over the max mark. The owner's manual states that it should be in between low and max. Could over filling cause rear seal failure? If so what's my alternatives?

It's either the rear seal or the oil pan gasket. I have changed several oil pan gaskets.