Assuming 120g KBS Tour shafts… As long as you’re using the same weight of grip and the same overall length with the new shafts, there wouldn’t be hardly any swing weight change. Maybe you’ll go from a D1 to a D0. If you think one swing weight point is that big an issue, add 3g of weight to the head when you reshaft or use a grip that’s about 5 grams lighter.
The MOI is a measurement of the club head itself, not the entire club, so it won’t change from having a different shaft.
As far as getting started goes… if you’re concerned with the differences of before and after, begin by measuring your clubs for length, swingweight, and total weight before taking the old shafts out. While the total weight will be different when you’re finished, the length and swingweight should be pretty close.