Motherboard BAT500 battery leak.

John Shelly, for now I would suggest to disassemble you phone, using this guide. Clean your motherboard and all other affected parts first with a backing soda/sterile water mix. Then use some high grade isopropyl alcohol and clean it again. As for evaluating the damage to your board, and if it is fixable, depends on which parts are damaged as well as your skill level. Post an image with your question so we can see what damage you have. It may give us a better idea of what you are up against. To add images to your question, use this guide.