03 explorer blown head gasket.

Our explorer has been showing symptoms of a blown head gasket, took to a mechanic to have it diag'd. He recommended a product called KSeal which is another one of those "magic" fixes. Put it in and it worked for a while. Now I'm looking at replacing the headgasket myself, and read that the sealant will harden up and clog coolant passages. This was about a month ago that it was put in and it's only been driven about 120 miles since. How boned am I and what am I looking at for repairs?