2000 Expedition Windshield Washer Fluid Leak

2000 Ford Expedition. Mileage: 97000 miles. V8. There is a leak in the windshield washer fluid system. The fluid leaks to the rear of the front passanger wheel well. I lost a full washer tank full of fluid when I found the leak. A mechanic friend told me the leak is probably inside the area below the wipers. He siad something like the sun must have gotten to some plastic piece. I haven't had a chance to look. What piece is he talking about? Is it easy to change? Is it cheap? Thanks.

P.S. If the tank had a leak the fluid would have leaked in front of the front wheel well, right? The fluid ran down the back of the front wheel well so this means that it has to be something else besides the tank, right?