You do not need a new filler panel to install Euro headlamps. The difference is all in the headlamp unit.

Wiring is simple - use the original pigtail. If you want the corner lights to be on while using the parking lights, you just splice together the city light wire and corner light wire - not the turn signal wire.

City lights are the small bulb next to the main bulb. They are used in the "parking light" position. If you are on a well lighted city street stopping & starting, head lights aren't really necessary.

Euros are easy to adjust. If you buy them from Katmac, they won't come w/ the vaccum adjusters. Just manually set them once & have done with it. I have a pair of Katmacs. They work OK. The glass is 1st class, but the connections and plastic housings are low quality.