You've got a lot of good advice here, personally I wouldn't spend the $10 for the stuffer attachment, I watched the video several times, I liked the music, the mixing head is turning, but..., watch carefully, "there ain't no sausage coming out of the stuffer," and that's the problem using a mixer or grinder with a stuffing attachment. You need three hands to make them work nominally, one to hold the sausage coming out of the tube, one to keep putting the meat in and one to keep pushing the meat back down the throat with the plunger.
Nepas made a good suggestion, if you're wanting to try sausage making without the expense, why not make fresh sausage, there are lots of good recipes, you don't need to cure it, you can boil it, grill it, cook it in a skillet with butter and apple juice or smoke it on you WSM.
The second problem that you will encounter is trying to maintain 140° in your WSM for 2 hours and then raising the temp 20°, I would suggest you learn how to do that before you try to dry/smoke cured stuffed sausages.
I don't mean to rain on your parade, just sharing with you what I have learned from my failures.