cam service tool

I have a '02 XLT 4x4 with 230K miles, this summer it has developed a timing chain rattle (chatter), and I want to nip it in the bud. This is my first 4L SOHC vehicle. My last ford was an '85 F150 with a 300 6 and 310k miles on it when it died, but that's another story... I have a few questions...