I’m always changing yarns, gauge and use this:
Input old gauge numbers, your new gauge numbers and it’ll calc your new no of sts. You can ascertain new incs/decs with the ‘Shaping’ feature (sleeves, necklines, etc).
Depending on the style of the pattern, you may need to graph out the slope armholes using orig nos and then regraph with the new nos. (Lots of sites with freebie knitting graph paper. Just input your old gauge on one, overlay new gauge and trace slope. Determine your new BOs.)
I’ve used this MANY times…works like a charm.