Changing a barrel isn't hard at all, but unless you're never going to be shooting that barrel again it's best to just get another upper, barrel wrench, upper vise blocks, handguard, BCG and CH, gas block &tube, and muzzle device if needed and build another upper. Be careful going down that rabbit hole though as the uppers multiply. I'm much like Lloyd in that I've got more than 15 lowers and have at least two uppers for each lower. Built a rack to store some of the extra uppers.
I have the M261 22lr kit. It works, the original 10rnd mags are usually the source of any feeding issues since they fit into a standard mag and there's more slop to account for. There are aftermarket high cap mags for it. In 30+ years of owning the kit I've replaced the flat tensioner spring 2x and it is a design flaw if you shoot them a lot. Next time I'll just replace the recoil spring guide base with one that incorporates a coil spring and lever/plunger which should last longer.