As i remember from installing mine there is a special barrel nut that is supposed to replace your barrel nut then the tube screws onto it. If thats the case then you'll need to remove the front sight for which you may want to purchase a taper pin punch from brownells (supposedly keeps you from mushrooming the pin heads), you'll also need new pins and a roll pin punch to remove the roll pin from the gas tube, and reciever blocks to hold the upper in a vise. Hopefully you don't have a brake or muzzle thingy permanently attached, if so you probably need to get it removed so you can slide the FSB off of the barrel. After you remove the FSB and gas tube use a DPMS or GI combo wrench to loosen the barrel nut and slide the nut off and replace it with the one that came with you FF tube, tighten per the TM. A strap wrench is a good idea for tightening the tube to the nut as well as some loktite. Reinstall the FSB, tube and tube roll pin checking for interference between the nut and tube and binding on the carrier key, adjust as necessary. Check zero and you're good to go.