If you buy a new header panel, the headlamps will bolt on. If you want to keep your 99-04 grille, you should do the cutting method. You will need:
Header panel
Head lamps
Conversion harnesses
speed nuts and bolts for attaching top of headlamp
If you decide to cut, then you need everything above minus the header panel
Here's a picture of what to cut (not my picture):
You will also need to drill the holes in the header panel for the upper headlamp attachment bolts, and you will see where to drill those after you cut and put the headlamp up to the truck, it will be 2 bolts per headlamp.
I would buy the new header panel. By the time you are done cutting the holes, you could have the new header panel bolted on, and if you are also converting to an 05 grille, it will snap in right instead of needing to be zip tied or something.