I think the two choices are replace or stop leak. To replace, I imagine you would need to slightly jack up the engine, support with a wood block under the pan and pull the mount to get at it. Pull the old plug, clean the hole thoroughly with water, let it dry and install a new plug with Permatex.

If the plug is otherwise secure and just leaking a little, some stop leak would take care of it. Not ideal but quick and easy.

My first choice would be a new plug.