At this point if you are running fine and not missing I would replace the plugs, top up the coolant and put a couple hundred miles on it and check that plug again. If it is bad there is a test you can do to the coolant to see if you are getting any exhaust gasses in there.
As for the oil at the Dist.-- If you have rubber arms you could reach down there and wipe it clean and check it with a mirror after a bit. If you don't have rubber arms just shoot some brakekleen down there and clean it off then check it. It's not something I would be too concerned about though.
**Update
Found this goofy guy showing the test for a head gasket leak.
http://www.youtube.com/watch?v=QA7KVQq9vKA
