These plugs usually start weeping after a couple of years. I've made it a point to get new ones whenever I change out the coolant. However, I've never seen one do more than weep a few drops at a time, so it is something that can be lived with eternally, if necessary.
I have this same leak at the bottom bolt of the fake fins and will try to get a replacement plug tomorrow. How does the old plug come out - just pull it out? Also, will coolant come flowing out while I'm trying to get the new plug in? Any helpful hints?