When I had the 97, I wanted to convert mine to the 99+ style, however I just traded mine in to get the 99. Anyway here's what needs to be changed:
- headlamps(with HID lights, ballast etc..)
- front bumper with chrome trim(and foglights)
- Front hood/grille/side fenders
- Side moldings
- Rear bumper with chrome trim/tail lamps

For the trunk, it is possible to use your 97 I THINK. If you notice on your 97 where there's the small chrome trim surrounding the license plate area... that can pop out(not sure how hard it is)..and can be replaced with the 99 style pop in with the fat chrome garnish. The only difference I noticed with the actual trunk is the small lip at the base of the trunk(where the trunk meets the rear bumper). Try look on ebay for closeup pics of various RL's.

That's just the exterior components. I'm not sure if any support systems behind the bumers etc.. need to be changed. If you do it.. the foglights can be wired the blank button you have to the lower left of your console.(That's where it is for the 99+).

Considering all this work, and the current value of the RL's.. it might just be cheaper to upgrade. There were over 300 modifications made between these two body styles. Major ones include side airbags, new steering wheel, stock HID's, different cupholders, and the agressive styling.

I grabbed my '99 a while back for $21K with 40K miles on the odometer. The KBB value at the time was 31K. The "true market value" is drastically lower than the KBB for RL's....they just don't hold their re-sale value. It's good for the consumer since you get a well built and reliable luxo car for a good price.

As for the housing.. I took apart everything. The chrome inserts just pop out in which I primed it a few times and coated it with black automotive paint. Hope this helps.