Very simple.
Pour a couple of ounces of ammonia in a jar, suspend a new grommet above the ammonia and seal the jar (I use plastic wrap). This will produce an aged patina in a short time.
As for the damaged hole in the shell, I've had success in this way:
Insert the badge/grommet combo in place, taping it TIGHTLY on the outside of the shell (make sure the badge is positioned correctly) and with the grommet facing up, carefully pour 2 part quick-set epoxy in the gap until it's just level with the shell - although I say 'pour', I mix the epoxy in a small paper cup and use a wooden match cut at an angle dipped in the epoxy and allow it to 'run' off the match and into the gap between the grommet and the shell.
After the epoxy is cured (I waited about 24 hours) I use a grommet tool to 'peen' the back edge of the grommet.
I've done this a couple times and it makes a very nice, almost undetectable repair.
Hope this helps.