Where can you find a diagram for the fuse box on a 2000 Mountaineer?

A cheaper and more effective answer is to go to the Ford / Mercury website and download the PDF owners manual. I own a 2000 Merc Mountie and the file was about 2.3 mb which took about a minute worth of downloading and abracadabra the information is there. Since you're already at your computer, you're halfway there. :> Go to Ebay and purchase an original owners manual for less than 10 bucks. The book will have diagrams on all your fuses. I just recently went through the same thing.