I would like to add the following tips for a cleaner install. I installed my own Shaker hood when I bought my car and would tackle this DIY in a minute.
1) With your hood heat shield off, measure, draw up your opening, and mask off. You need to use a saber saw. This prevents 90* corners.
You want rounded corners.
2) Next, use a large drill bit to start off somewhere near one of the corners. Use a liberal amount of masking tape as the saber saw's metal base will be sliding on your shinny hood. Drape the whole hood, frontend, and fenders with newspaper. I hear it's still cheap.
3) Once you have your nice opening drawing down and your starter hole just follow the opening drawing you've drawn for your self on the tape. Go slow, it's not a race. Loosen the the blades rotating function on the saber saw around the corners.
4) Now you should have a nice hole in your hood. Scary. Semi-reinstall the heat shield. With the hood somewhat open, take a Sharpie and outline the hood opening onto your shield.
5) Remove heat shield. Poke a nice hole in it with a knife near one of the corners. Next, use GOOD SHARP scissors to cut where you traced your hood opening. Again, take your time doing this.
6) Reinstall heat shield with all the fastener and reconnect the windshield wiper fluid hoses if you removed yours.
7) You're almost done. Go visit the idiots at Auto Zone or some parts store and find a nice piece of trim. You're looking for one that is extremely flexible. An ideal one would be like the one from a door seal or the kind they use around the edge of a heat shield on an aftermarket CAI (Steeda comes to mind...). If one side of the trim is larger than the other even better!
8) You want the larger side of the trim to go over your heat shield side as its not a perfectly flat surface in some spots. Start in the center rear (or center bottom with hood up). The trim will tend to conform to round corners more than 90* corners. If the trim seems to want to work it's way out, apply a small amount of Marine Goop to the few areas of concern. Make sure the trim is all the way on there before you cut off the excess. You're done.
The above should result in a clean and hopefully professional looking install.
Good luck all,
Gerardo