Nothing is as easy as it looks!
If it doesn't bother you, drive it. If it does, you'll have to pull the head to see what's going on. While you have it out you'll probably want to have it done. That will lead to other things and other things will beget more other things and the next thing you know, you'll be doing a total rebuild and will have spent thousands of dollars to simply find out what was wrong with #6.
Spark plugs and oil can be inexpensive when compared to a full rebuild. Doing only the head is like getting to first base on a hit and then having the game cancelled for rain. It was good initially, but in the long run you'll wish you had run all the way to home plate.
You could luck out and just replace the head gasket, but after reading this page for years, I doubt that's the problem. Read the post linked below about Tony's hell to find out how small things somehow just keep growing when you start tinkering.
Horror Story Part 1 Horror story Part 2 Horror story Part 3
