Is this a MKIV or MKV GLI?
Headlamps nowdays are made of polycabonate plastic. They will yellow and fade when exposed to UV rays from the sun and there's no cure for this. So your only options are to replace them or use the Meguire's or 3M headlight restoration kit AND protect them with something like Lamin-x covers (www.lamin-x.com). Some aftermarket companies have started to produce glass replacement lenses you can install yourself. For the bottom lip repair, the call is yours although I think both of those repair otions are way too high. Check other body shops for pricing. Personally I'd try to source a used one from a junkyard, the classifieds on Vortex, or craigslist pay to have it repainted and then install it myself. But if you have marks all over the bumper, you may wish to install it and them have the whole area painted.