I noticed the right side low beam wasn't working on the wife's '03 X5 3.0 as she backed out of the garage this morning. She confirmed the check low beam message was displayed during her drive to work. A google search turned up a number of hits for replacement bulbs. Some sites, like bimmerzone.com, included the following in their Sylvania Xenon D2S Bulb product description:

When replacing the Xenon bulb, both must be done @ the same time. The Xenon bulbs change color with usage & time, hence the reason why one bulb will appear yellow & the other 'blue'.

Is this a tried and true fact, creative advertising, or best practice? This is the first vehicle we've had with HID so not much experience in this area. I've never swapped out multiple halogen bulbs when a single bulb failed. A search of the forum didn't turn up any posts supporting this claim.

Does the entire head light assembly need to be removed from the car to change the bulb? I admit I haven't peeked under the hood yet, but Zulu95's Changing E53 Xenon Bulbs DIY shows the entire assembly removed.

Is there a preferred bulb brand? I plan on sticking with a standard 4100K bulb.

Is $114 a bulb a decent price?

Thanks for the help!