I disagree with one point of your post: Go ahead and enjoy your rifle! The AR-15 is an enjoyable platform with little recoil and very accurate to 300-500 meters. With dedicated care and cleaning/lubrication, it's a reliable weapon system. From my own experience, other than inadequate cleaning/lubrication, the magazines are the weakest point of the AR-15 design with their tendency for feed lip bending. PMag makes a great robust AR-15 magazine, however, in both 20- and 30-round models.
So go ahead and have fun with your AR-15 while knowing the skills you're practicing may come in handy "in case of zombie invasions"! I enjoyed both shooting and working with mine so much, I went ahead and built a second Vietnam-era retro version from excess parts. :-)
Oh, and I recommend you visit AR-15.com for a great source of on-line info.