I didn't do couch to 5k, but I did start running and have run a few 5k's, and 4 & 5 mile races. No improvement to my cycling and in fact, cycling suffered as I ran more and cut back on cycling. I'm back to a better balance of cycling and running. As for weight loss, I took up running to lose weight, but there hasn't been much weight loss, but that's 100% due to me not cutting back enough on food. Weight loss is always fewer calories taken in than burned and I haven't been careful at all w/ the calorie intake. I haven't minded either. Those calories tasted good.

As for shoes, since you're pounding on your feet, treat them right and get fitted for a proper pair of shoes. Then replace them every few hundred miles. The goal is to run injury free.