Don't do any cutting just yet. Give yourself some time to be sure it's what you want. Kind of a "measure twice and cut once" deal.

As for the cramping--be darn sure you are taking in enough fluids and, if you are sweating a bunch, potassium/sodium like has already been suggested. I believe that cramping in usually a sign of lack of minerals. Also, the stretching will help.

As for the derailleur adjustment: it, along with things like fixing a flat and adjusting brakes, can be learned by watching YouTube videos. There is a ton of good instruction on there. For me, I have to be able to see how it's done before I can learn it. One word of caution: for any repair you want to learn, watch at least 2 or 3 videos. Most of them I have seen are fine but occasionally I run across one where the guy is teaching something completely wrong. If you watch a couple and they agree on how to do something then you should be fine.