I did mma about ten years ago. It was a lot more popular at the time, especially local amateur events. We would get crowds of over a thousand people, which is a lot for a small town.
K1 is the other kind of kickboxing, as opposed to Muay Thai. The latter has the clinch, and no takedowns. In k1, sweeps and I think even throws are allowed, but points are not awarded. It is pretty cool though to dump someone on their butt while the are standing on one foot trying to kick you. Just kick the ankle they are standing on.
Both k1 and mt shin kick to the thigh. That is the best kick to master and the most realistic to land in a real fight. We would rest a heavy bag on the mat, held by a partner. Then you shin kick and drive through the bag, moving it each time, alternating legs as you move it down the mat. The idea behind power in striking is that you displace space. You strike through the target. Point sparring arts like tqd and karate have a lot of moves that strike with very little power, because they are point sparring. It looks cool, but little slaps dont help in a real fight (unless you hit your opponent's nuts)
Keep your chin to your chest when sparring. Blows glance off your forehead instead of landing on the soft spots of your nose and throat. If you are worried about looks, try to not get your ears mashed up. Some guys are just more prone to cauliflower ear. Fluid has to be drained right away if you get it, or it never looks the same again. Those helmets dont do anything at all to keep you from getting killed, but they might protect your ears. Also, make a habit of covering your skin when you can, to avoid rubbing bare skin with another sweaty guy. You don't want mrsa.
You'll get in great shape, and in all likelihood actually be less likely to get in a bar fight, compared to someone who doesn't train. Good luck with everything. Take it slow, stretch and warm up a lot before training, and learn to relax instead of being tense. That is how to avoid injury and keep at it.