Get a vest pattern, remove the backing from the stole, watch to see how it is sewn together so you can copy the seams when you sew the pieces together.. When you cut the fur, try not to cut the hairs around the cut by smoothing them away from the cut as you cut. If the leather is thick, you may need a heavy duty sewing machine. Good luck - great idea, and a challenge.
Very good idea from 2dogal, visit any fabric store like Joanne's for vest patterns. Plus you'll have a pattern for future sewing projects.
Aid,. Start with cutting off the arms and make a hem. Shorten the bottom, and put a hem there. Aloha!