I have a 2000 Discovery II. I just recently did the 03-04 headlight and grill upgrade. I purchace a cd-rom guide off of eBay for around $50.00, the guys email is email@example.com
. I highly recomend buying one of these. It has detailed instuctions, parts list and photos. It is definitly not just a bolt in swap. You will need to cut some sheetmetal behind the headlight with a small hand grinder with a 4" thin cut off wheel. The early wiring does not plug into the new lamps so you will have to cut off the plug and splice in new wire to the lamp. Its not as scary as it sounds. I prepared the wiring in the lamps, bought the touch up spray paint for the new finishers and got all the tools ready. Once you cut the sheetmetal and the wiring there is no going back to the old lamp so you need to have everything ready before you start the swap.
The headlamp level adjust motor is bullt into the 03-04 lamp. There are 2 different versions of the new lamp with or without level motor. My rover did not come withe leveling option so I bought the non leveling lamp. One way to tell which lamp has the motor, the non leveling has 7 pins in the wiring plug and the leveling model has 9. Be careful buying used lamps off eBay, because some people sell waranty return parts. I bought a pair for around $500 and they both leaked. I ended up buying a new set. It was worth doing the swap. I like the look of the new lights and grill much better and it increases the value. Another thing I did was install 03-04 tail lights in the bumper, with the clear and red lense. I used an amber bulb in the clear side for the turn signal.