Pull up the carpet and check your floors for rust first. Don't get discouraged if they are rusty, most of us have had rusty floors in our MJs before. As said by Tim, get yourself a Renix Engine Monitor, seriously, it will be a lifesaver. Check out the link in my signature for a write up on the 3ish inch lift that I did on my blue MJ (see my profile picture or cover photo if you view my account). You could pick up 2 inch spring spacers and do an Add-A-Leaf like what I did in the link in my signature pretty cheap. Add some WJ Grand Cherokee lower control arms, and you will be able to clear 31s easily.
Welcome to the addiction!