Can't comment specifically on the 380SE, but if your transmission pan gasket is a thick rubber thing with a groove that fits over the pan lip (like my '82 300D) - then you can definitely split it by overtorquing the pan bolts.
In fact my transmission was slowly leaking fluid due to the old gasket having been split at some point - either with age, or more likely due to an overtorque situation. The pan bolts don't need much torquing - something like 12 ft-lbs comes to mind. Just snug, not too tight.
Maybe someone with a reference can give you the proper torque, and I think you'll be OK with a new gasket. And hopefully they can explain the washers & seal.