Install is a bit hairy, but do-able with some patience and time.  The SLP instructions are good for the airbox part, I should just mention that for cutting the airbox portion, a rotary tool is great.  Make the cut with a cutoff blade (reinforced one will do the whole job, regular will wear down pretty quick), then make it clean and even with a sanding bit.

Now, the radiator shroud is the hairy part.  To remove it, pop it off the 2 retainers in the middle first (the two visible from the font of the car with the hood open, two white circles).  To do this get under the front of the car, slide your hand between the radiator shroud and the other plastic piece, and just pry them apart.  Now, at the bottom left and right of the shroud, there are two "ears" that stick in two indents to either side of the A/C unit (the rear, smaller version of the radiator).  Pull the ears off their retainers, just grab and tug. 

Now, to remove the shroud, you must protect your A/C fins from being bent.  I used a piece of cardboard, slide it over the A/C fins.  Then pull the "ears" in toward each other, this will make them bend about 90 degrees, and lay against the cardboard.  Now you basically have to pull the shroud out a few centimeters at a time, each side (pull left up a bit, right up a bit, repeat, etc).  You pull up from the top a bit, then reach down in and unsnag it, then get under and push some, then pull the top again, etc.  In other words, be patient, and it will eventually come out.  At one point I even had to bend the shroud a bit and be a tad forceful with it, but just don't push it up against the A/C unit too hard.

Now, when you finally get it out, drink a beer (to increase your measuring accuracy).  Then, measure along the slit at the top of the shroud, and mark where SLP shows in their instructions.  Now hold the CAI up against these lines, yep, they're inside the edges.  Just center it so that these lines are the same distance from each edge, then remark the new lines, give it maybe 1 millimeter outside each side of the CAI.  As far as the height of the cutout, SLP's blurry picture looks like it says 4 or 4.5 inches.  I cut it that much then reinstalled the shroud, tried to fit the CAI, no go. 

Took it back out, this time cut down to the ridge that is about 3/4 of an inch or so lower than the 4" measurement.  Anyway, once its marked properly, extend the lines so they connect and make a rectangle, then go at it with the rotary tool.  Now to reinstall the shroud, do the same procedure in reverse, cover with cardboard, fold ears in, and nurse it back down in a little at a time.  On the way down make sure it is on the engine side of the plastic piece with the two retaining clips that you pulled it off of.  It wants to try and go in front of it, but obviously this won't work.  Once it is all the way down in, re-secure the 4 clips (2 ears and 2 in the middle). 

From the top, hold the CAI with the bottom opening toward you.  Tilt the top toward you so the bottom opening is aiming down at the ground, insert into the hole in the shroud, let it go down until it rests on the bottom edge of the opening.  Reach down in and pull the bottom edge of the opening toward you, now the CAI fits right through it.  Now carefully lower it, angling it back away from you as you do.  Basically, during the whole process, you are trying to not scrape the A/C fins on the way down.  It might be easier to have a friend under the car to help you (note you need 2 beers in this case), but I did this step fine myself.  Once its down in there, snap it over those same 2 middle retainer clips, drill the two screw holes, attach the weather stripping (all that is in the SLP directions), put it back together, and you're good to go.

Note that with this mod, you should have an oil coated filter, like the K&N or the Holley, not only will it let more air through, gaining more power from your CAI, but it will stop small amounts of water and dirt from the CAI better than a paper one.  Plus, the CAI does attract more dirt and dust, so a cleanable filter (either of those two) is going to be cheaper in the long run.

Above 40 or 50 MPH you should now notice a slight whooshing air sound, and increased acceleration.  Of course this mod only gets better with the airbox lid, air bellows, throttle body, etc.  MAF and MAFT, as long as they're put in at the same time and adjusted with Autotap, will also make the CAI work better.

Another note, if you have a non-Scoop car, install the seal that SLP includes.  For Scooped cars, you have a choice, if you install it, you are pressurizing the box (possibly a very slight supercharging effect), but giving up the large amount of air from the scoop.  If you don't seal it (as SLP recommends), you take advantage of air from both over and under, but a lot of air is lost to the engine bay, and warm air from the bay can get in there.  Right now mine does not have the seal installed, but this spring I will make a few runs each way and see if there is any difference.....