1) Yes you can do it by yourself with a grinder, I would make sure I have 2 things in order to do it easier. first would be a foot pedal, they are cheap now, and hey I won't tell if you steal the one from the wife's sewing machine. Just clean it up well before putting it back. Also a kidney or stuffing plate, a lot of grinders will come with a thin metal 3 spoke piece of metal. They have worked for me if my sausage was finer ground and on the wetter side, a kidney or stuffing plate will be the same as your other plates and be stouter. As mentioned keeping the table wet will help you control it as it is coming off the horn.
2) I have used some of the old hand crank stuffers, like the enterprise ones, still have one or two here some place, those were mounted to a table via bolts usually or to something like a 2x8 about 4-6 foot long, then clamped to a bench or a set of saw horses, and depending on your work area I have seen people have someone sit on the ends of the board. I have an old cabales (Weston) 11 pound I believe, it has a gear reduction and it is fairly stable on a table, I also have a motor for on it along with a foot pedal making it nice because again you have both hands free to work. I have never used one of the horn type stuffers, the ones you put the meat in the back of it and it has a handle to push it through.
3) Depending on where you live grocery stores will sell casings and even some seasoning mixes, hunting is still big around me and a lot of hunters will process their own deer. If you have a butcher shop or meat market you could probably get them from them, also some areas have butcher supply stores, they have every thing from seasonings to the equipment, you only need to supply the meat. Also online, The Sausage Maker, Allied Kenco, LEM, and Amazon just a few places to look.