Ebay parts
#2
guess it depends on the parts your buying and who manufactures them. You can get oem parts a little cheaper. If you just doing general mait on the car I would stick to oem parts. Ive bought things like wheel bearings/hubs , rotors/pads with non problems. I bought all 4 rotors and ceramic pads for my lincoln and it only cost me 100 bucks. Id stay away from things that seem like they are to cheap and are from china like heads rockers and internal stuff.
#4
1) Select U.S. only for origin of the part. No, it doesn't mean the parts won't be from Mexico or China or wherever but, if they try to screw you in the transaction or you're not happy with the parts it's more likely than not that you can get your money back or an exchange. If they are shipping from China or wherever, good luck.
2) Look at their rating and buy from those that are at 99.4% or better and have a preferred seller (gold/blue ribbon). They usually communicate well and try their best to resolve issues.
3) not just for e-bay but any place. For any brand of aftermarket or even OEM headlights, always use clear windshield RTV or clear flowable RTV to seal the seam between the clear lens and the body of the lamp. Trust me on this. Over the years I've used both OEM and aftermarket headlights on everything ranging from Ford and GM to VW and Honda, they almost always get condensation in the headlight if you don't do this. Once the condensation is in there, it's nearly impossible to remove without leaving some sort of trace on inner clear plastic lens. You can see just how bad the seal is on headlights when you apply the RTV and you see it filling in all the gaps that go all the way into what's supposed to be sealed.