Welsome to the site! You'll find everything you want to know about your truck right here. Welcome abaord!
The corner lenses on the 95+ models only have 2 retaining screws. When you open the hood and lift the little flaps on the sides, you'll see 2 little Phillips head screws (2 per side). Just take those out and pull forward. Wiggle the housing side to side a little. It might be hard, but it will come out.
About the guages, check out our newly created "Useful Threads Forum" for a thread detailing the install of indiglo guage faces in a 98+ Explorer. It's a great thread, including pictures, and it will help you out.
