Depends on your definition of "big" and "simple". It's definitely something you can do yourself, but it requires a bit of care. The only tools you'll need are a hammer and punch, an AR armorer's/barrel wrench, vice grips, maybe some snap-ring pliers for the snap ring that holds in the delta ring spring, and maybe a 1/2" socket wrench to help you get leverage on the barrel wrench (that little chunk of metal doesn't provide much of a lever when you're trying to get the barrel nut moving). Just disconnect the gas tube, undo the barrel nut, pull the barrel, put it onto the new receiver and tighten the barrel nut, reinstall the gas tube, and put the handguards back on. You may have to do a bit of fiddling to get the barrel nut, delta ring, etc. all lined up (obviously before you start you should look up an actual guide to those procedure, not just follow my halfassed outline).