The yellow boot just turns off counterclockwise, and you just thread the new one on. I tore mine pulling the plug wire trying to install the sensor wire for my TT Vapor. Definately don't need to replace the coil.
I tore mine too. I have yes to replace mine and actually used high-heat RTV to put it back together. I (as of yet) have had an issue with water and it shorting out and I've been up to the intake with water on it.