1. I'd file the end fittings on your new shift cables until they'll fit into the little pockets in your shifters. It shouldn't take too much work to make them do that.

2. Unless your shift housings look really pristine, I'd replace them. An LBS will have bulk cable housing and a supply of the little metal ends. The housing diameter doesn't matter much. After you cut them to length, be sure to get rid of the little metal burr that will stick in where the cable goes.

Fresh cables and housings will definitely perk up your shifting.