it is fairly easy to remove it but it will require you to buy a special female torx bit to remove it. i think it cost me 5 or 10 dollars to buy mine at carquest. it is made just for GM ignition switches. if your just replacing the lock cylinder, then you will not need this tool
tilt your column all the way down, then pull the plastic piece of the handle that you just used to tilt your column. next remove the 3 or 4 screws from underneath you column so you can separate the 2 pieces. to get the top piece off to remove the lock cylinder, i took a pair of side cutters and sniped the cover just below the lock cylinder. i couldn't figure out any other way to get the cover over it so i just cut it. you can't tell once it's back together.
anyways, if i remember right you need to insert the key and give it a quarter turn, then insert a pick or awl in the small hole to release the lock cylinder.