Update at bottom of post
Seeing as there's no actual thread that details/documents A) what to buy and B) how to install this, I figured I put this here.
I came from owning a 98 XJ, where the headlights sucked, but the upgrade was easy enough with a new wiring harness, new H4 eCode lamps, and Hella H4 bulbs. It was straightforward and easy to install. And that's what I was expecting with the WK.
Lets be fair, the low beams on the WK suck. Thankfully you can get some Philips 9011 series 3000 lumen bulbs that are easy to modify to fit in the WK.
-a flathead screw driver or knife for the plastic rivets (or a plastic rivet remover, which I highly suggest)
1) Buy the bulbs
. I used rallylights.com (Susquhanna Motorsports) for these bulbs.
Warning: If you're in Canada/international, Susquehanna uses UPS, so you'll have to wear a $40-$50 brokerage/duties charge. Make sure you ask for USPS, it's almost a guarantee that there'll be no charge. It'll just take longer to get the package. Update Jan 2015:
Susquehanna now offers USPS in their check-out, you no longer to specify it. When I ordered, I bought 4 bulbs to lower the average cost when including shipping and duty/taxes. For my 4 bulbs, I paid around $15 in taxes/duty.
2) Modify the new bulbs. The red area is what you need to remove. I used an 8" metal file.
If you are only replacing low or high bulbs, you may skip steps 3, 4, and 5. It's a tight fit, but if you're careful, and you contort your hand you can remove and re-install the new bulbs without much of a fight. However if you plan on removing the headlight unit proper, you'll need to remove the bumper as there is a plastic tab that prevents easy removal of the headlight unit.
3) Open your hood. Pull the plastic rivets holding the grill. Pull the bumper. There's, IIRC, 6 metal screws (1 on top, 1 on either side in the wheel wells, and 3 below the bumper attached to the plastic skid) and several plastic rivets. This'll take some time, but if you're careful, it'll be okay. I tried using the Factory Service Manual, but that only told me where the headlight unit screws were.
4) Pull the black "skeleton" bracket that's behind the bumper. It's secured by 2 screws.
5) Unscrew the 3 screws holding in the headlight unit. You'll need to jimmy the light out.
6) Twist out the old low beam (Lows are on the outboard side above the turn signal)
7) Install new lights. On the left is the new Philips bulb, with the old grey bulb on the left. The old ones (on the left) and the new Philps bulbs use rails inside the light to slot into the headlight plug. The new ones, because they use 2 rails instead of the stock single rail, will need some force to fit onto the plug. Rest assured they DO fit.
8) Enjoy brighter lights! With the greater light input, you can really see how sharp the cut-off is from the lamp unit itself.
Update Jan 2015:
The bulbs burned out on me, about a week apart from one another. So I got just over 2 years of usage out of them. I also discovered that removing the bumper was made exceptionally more difficult by having the 4XG front skid. To get at the 3 bottom bolts on the bumper, you have to snake a wrench through the opening slats. When I saw this, I figured I'd give it another go with contorting my hand to change the bulbs, as per several users who very politely (
) suggested that there was absolutely no need to remove the bumper, if you could contort your hands.
So, to change the high or low bulbs, there is no requirement to remove the bumper! However, if you want to get access to the headlight unit proper - to remove it - my experience is that bumper removal is still required.
My DIY walkthrough is still pertinent (up to step 2) as I show a comparison of the bulbs, and which bit of plastic needs removal for successful installation in our WKs.
This is an easy upgrade, one that I would very highly recommend to all WK owners.