How hard it is, is really dependent on your skills with welding, metal fab, and sheet metal work. If you dont have experience with that, like a challenge, and have good problem solving skills, you should be able to do it. It is a "job" IMO though.
I was able to do mine by doing research on this site and other sources. Do lots of reading, get educated first. One thing I can tell you is to brace and measure before you start cutting things out.
Oh, and if its really bad on the bottom, you may have to do a section of the inner rocker where its pinch welded to the floor brace as well.
This site can get you through just about anything you need to do on an EB. It will help you tremendously if you become a contributor so you can post pictures along with your questions. Like right now, you could post a pic of the post. Being able to look at it can rule out repair over replacement, just a thought. Way to hard to describe things in text sometimes.