I bought some new black letters to replace the silver Land Rover letters on the hood. What's the best way to remove the silver ones?

 

I use WD-40 and get around edges. WD dissolves the adhesive, does not scratch paint, can be clean off with mild soap. Spray edges and slowly peel back, carefully not to tear decal. Use as much spray as needed. DuPont makes a decal/adhesive remover which is good, but WD is cheaper and usually on hand.

 

Ditto above...

And dental floss can also be useful for making the initial peel of each letter.

 

I was thinking more along the lines of a falling tree or a scrape with a boulder. but those other comments are good too.