For the lenses just keep them waxed and they'll stay new looking as for the black trim Mothers and Meguiars make a trim treatment that works real well
Yes. The same polish & seal/wax you do to your paint, should always be done simultaneously on the lights. Preferably, the most hearty sealant/wax you have, post the cleaner polish every once in a while on them, for the best protection.
There are some cases where the lense plastic is less than stellar and yellows/hazes regardless of care, but that hasn't seemed to be the case on any GM vehicles from the past few years when they're at least decently cared for.
You don't need any treatment beyond this, such as the drill attachments and harsh polishes, unless it's too late and you're already into the yellow fogged stage. Polish & seal, and you're good to go.