I know you are only questioning how to replace the lowers. But while it is apart I highly recommend the progressive mono tubes as well. No more change fork oil. And definately the front end is more stable on washboard roads. jmo

 

FYI, I've only ever done a few of these but I've never needed an impact wrench to remove that 6mm allen head on the bottom. Just a good allen wrench and a little rap with a hammer to break it loose has always worked for me.

 

The pics and procedure in the book can look intimidating. Years ago I was afraid to try it so I paid a shop to rework mine for $500. Next time I did it myself and took a few hours total, each time got easier and faster. Last one I just did took about 30mins including R&R (minus front wheel).