No modification necessary, however unlike the Hella's, the backs are plastic. That's why they say 55/60Watt only, the brighter ones will warp the reflectors. Just pull the sealed units out and plug in the conversions with the bulbs mounted in them. Just make sure you only unscrew the 4 mounting screws, not the 2 adjustment screws.
I don't work for Whtney, but they were the cheapest, approx $75 for all four, and offered free shipping on all lighting. Same reason I got the bulbs from Amazon, probably due to stories about the depression from my Mother and I'm Scottish.
The Speaker's are cool and expensive. I love the LED feature, but if it goes out you usually have to replace the Whole unit. I know you do in BMW's and Mazda's. They're usually pretty good, but the are electronic (diode). FYI...I've never had to replace an HID bulb (approx $125 ea) in my years as a Parts Mgr.
The Painless kits are great. I've used them to put ridiculously large driving lights on my cars. I wire them to come on with my high beams and I've never had one fail. I've got a pair of enormous Hella 700FF's that I'm putting on the AS as soon as I get the short fixed. The small rusty yellow fog lamps supplied by Airstream are being replaced by 160MM round yellow Bosch fog lights. It will look like the worlds largest Rally car, because I've noticed that as I've aged the nights have gotten darker, the moon dimmer, and the printing is all fuzzy...I'm just saying.
Pic's when I'm done.