TexasCHLforum.com

This is just my experience as a new AR owner. You might want to try the arms room. The armorer there might be able to help you out (call first and ask to avoid making a trip. Although, a trip to the arms room is always fun). The only reason i suggest this is i had a lot of trouble removing mine for the first time on my new ar. I bought a wrench and tried to remove the castle nut, but i ended up taking my receiver back to the vendor i bought the wrench from because i just couldnt get the castle nut loose. That thing was on there really tight. I ended up with several knicks around the nut and threads that remind me of my efforts. Mine wasnt staked but i think there was some form of loctite on there. I even took a blow torch to it to warm the nut up slightly with the hope of loosening the loctite. The shop owner had to use a beefed up wrench to finally break the nut loose. Now, i am able to use the wrench i bought since i didnt have to torque that nut down as much as it came from the factory.

There are a couple of youtube videos that show the exact steps. Once he broke the nut loose, i was able to do the install myself. Also there are a few stickies on AR15.com that describe the process step by step with pictures.