It's not really hard. Leave the lights in for sanding and polishing leverage, but tape off so you don't hit the rubber seal around the headlights or the paint. Then pull the headlights out and spray them. If the rubber seal around the headlights are in good condition, remove them before you spray the headlights and back on when you're done. You will have a big grin on your face when done and a great feeling of satisfaction of the job you did.
You should be able to get everything at like O'Reilly Auto Parts. This is the Polishing Pad I use.