For the headlights, depending how bad they are, you can use anything from a mild polish like the one pictured above, and go all the way up to wetsanding/polishing if they are real bad. Just depends how bad they are and how perfect you want them
I'd be very cautious using plasticx on the interface though. I'm not too familiar w/ the actual material used on the interface, but if its like any other I've seen, they are relatively soft and susceptible to further scratches from a abrasive product. If its real bad, talk to the dealer about a possible replacement. To keep it clean, typically a microfiber glass towel dampened w/ distilled water or optimum no rinse will keep it clean, however not remove any swirls/scratches.