leave it alone the bigger chance is your only going to ruin it. Dye wont get rid of the pattern of patina and wear around the decals, you don't know what other things like conditioners or water proofing have been applied that may effect the dying process and you still have the liner to contend with that will no doubt get stained in the process from small wear holes or loose stitching. Enjoy that beautiful coat and existing patina for what it is or sell it and buy a black leather coat. Sorry to be blunt but i see a wreck coming.