Some pretty good suggestions. I rebarreled my DD M4V5 to a 14.5" barrel, so I had to remove the gas block in order to get the barrel nut to slide over the muzzle. My gas block was pinned...had a taper pin, and it was on pretty good. Took a bit of force, but I managed to get it off none the less, with the use of a hammer and pin-punch. Worked it both ways at first, a little at a time, and lubed it in the process of doing so. I was eventually able to get it off with zero damage or markings...needless to say, I was quite happy with the end result.
Whatever method you do decide to use, just make sure that you use the proper tools, use the tools properly, and do the job properly. Have patience, and take your time. There are some pretty good instructional videos on YouTube that you can watch to gather a few tips, or to see a few different methods that may not have been mentioned. In any case, the more that you know about the task you are going to take on, the better off you will be at achieving the results that you are expecting.
Good luck...