How to prep paint for decals/emblems?!

[91LXConv]

1) My car is a 1991 red (original paint) 5.0. I'm removing the factory-glued-on"5.0" emblems from my front fenders and replacing them with new stick-on "302" emblems. I have them off but some old factory glue is still on the paint. How should I safely remove the old glue and prep the surface for the new emblems?

2) I'm also adding two small white "302" decals to both sides of the small factory hood cowl (painted surface). How should I prep the surface for the decals, and how about after they're on?

PS- It might be worthwhile to add that my car will still have about a 2-3 week old coat of wax on it when I add the emblems and decals.

Thanks for any help!!!