They're relatively cheap -- about $30 bucks or so. Click on the fastlane tab above and look for it.
Remove your old one with a putty knife and some adhesive remover. Lay down a sheet or other cloth over your engine to protect it. Don't use plastic because the adhesive remover will eat right through it. Then spray the hood with some heavy duty 3M spray adhesive (#9?), then just slap that new pad right on and smooth out the kinks.
It's pretty tough to do it alone because you get one shot to throw it up -- doable though. Better to have an assistant help you "wallpaper" it up.
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi