Don't use that stuff, it is crap and is bad for everything else! Sorry to say but a cracked head means replace the head. Unless the crack is in a spot where you can weld it but even then its a shot in the dark. Luckily heads aren't too expensive out of a junkyard. There are many options but if you just want to replace what you have there are tons of write ups on here and google that could help you along. You should also buy a Haynes or Chiltons manual so you can learn as you go.
As for the radiator, there are repair shops just for them or scrap it and get a new one. Welcome to the jeep forum!