Casing isn't that difficult, but if you are using the KitchenAid for stuffing, that is a pain. They don't work well for stuffing.
Grinding does take its toll on the mixer as well. The plastic gears and motors in them now just aren't made for that.
Storing casing afterward isn't an issue. Just make sure you dry any of the ones you soaked, and then re-salt all of them. Seal the bag and back in the fridge. But fresh casing, find a butcher that makes their own sausages and just buy casing from them. I can get the tube of casing in both 22mm and 32mm for $5/tube from them locally. A tube will do about 10 lbs.
For breakfast sausage, the collagen casings work the best, and they keep a very long time if they are stored right.
Our Super Store sucks for selection and quality. We have a Fairways Market that deals in a lot of Asian foods and caters to their meat selection. Usually, some good stuff in there, just not convenient to get to. We have Thrifty Foods here, which was bought by Sobeys. They still have good quality meats, just have to pay a bit more to get it.
Our Save-On is hit and miss, and usually I am just there for sales on BBQ meats.