[RMSLS02]

Just the bulbs? You can get a pair of D2R (if you have projectors) bulbs from ebay for under $100.

Now thats assuming you have projectors headlamps, and assuming all you need are the bulbs. Balasts would be a different thing.

If just the bulb is burned out, I recomend Philips bulbs rated at 4300k (Which is OEM standard rating for all USDM cars with HID's.

 

[RMSLS02]

Ok, Hang on a sec. Do you have a 99 STS? If so, there wasn't even an option for HID lighting.

So, you're just looking for Whiter/Bluer bulbs, correct?

If thats the case, you can get bulbs for much cheaper.

I would search on Ebay for "9006 bulb"

Some companies I've heard good things about:

PIAA
HELLA
SYLVANIA (OEM) -Search for Silver Stars
NOKYA (These would give you the bluest tint I believe)

 

[RMSLS02]

How much possible is simply pull out halogen lamps assy and mount in 2002 STS HID assy into 98 STS?

I belive they should swap out perfectly. the only thing is, you'd have you buy the whole headlamp assemblyso thats the headlight housing, new bulbs, possibly new wiring, ballasts and bulbs. this could be expensive.

 

[RMSLS02]

A blue bulb won't give you the most light though. It may look brighter, but going through the filter to make it blue will cut down on the amount of light that actually makes it out of the bulb.

The HID headlamp assemblies from a newer Seville will fit, but they are veery expensive, because they include the bulb and ballast assembly. If your really looking for HID's, I would suggest a good aftermarket company. They are easy to install, and are very reliable, in most cases more reliable than OEM equipment. That what I did on my 1998 STS. Also, if you do go for HID's, they are different temperature ratings, depending on how much light you want, and what kind of color. The coolest bulbs (i.e. 4-5000 degrees kelvin) will produce the most actual light output, and will be very white. The higher you go in temperature (i.e.7-8000 degrees kelvin) the bulbs will produce a blue light, with a little less intensity than the cooler bulbs. At the end of the scale (i.e. 12-14000 degrees kelvin) the bulbs are now producing purlpe light, and have much less intensity than their cooler counterparts.

What Temp did you get? I got a Gen III Slim Balast Kit from Philips at 6000k