Before buying the xenon bulbs you should switch them to see if the bulb is really bad. The xenon bulb usually will last longer than the car. Anyway, 99-01 Q's use D2R, not D2S (D2R is used for reflector headnight, D2S is used for projector headlight). D2R has a speciall paint stripe on the bulb to prevent glare. They also have different cuts on the base so a D2S won't fit into your housing unless you modify it.
$73 is a decent price. Replacing them is simple just like replacing regular bulb, a 10-minute job. You'll need to remove the battery to have access to the right side assembly though. No need to go to the dealer.
http://faqlight.carpassion.info/hl-hid-bulbs.htm