It's messy, but pretty easy. Old sheets over engine and front fender/grill area to "catch" debris. Tear off what you can and scrape the rest of the pad+adhesive with a dullish putty knife. Use 3M adhesive remover on remaining adhesive. Clean and dry area. Use 3M trim adhesive (they make a spray can version) and follow directions on the 3M can or tube (if you use that).
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)