13MM sockets (deep and shallow). I used 1/2" drive, but those of you who have some serious muscle you could use a 3/8".
Misc. extensions. If you can make a chain of extensions a couple feet long it can make your life easier.
PB Blaster. Lots.
Impact wrench (optional, I didn't use one. Might make life easier, but also might snap the bolts easier).
A mechanic or the necessary tools to remove a broken bolt.
New crossover (obviously). I got mine for free when I bought a pulley puller from some guy.
Crossover bolts. You might get lucky and not need them, but the extra $10 is good insurance in case you do.
Alright, first off you're going to want to spray the living crap out of all 4 bolts that attach the crossover to the manifolds. I used PB Blaster, but WD-40 should also work just fine. I'm not kidding here, soak them. Let them sit for a day or two and soak them again.
Next up depends on weather or not you have a custom intake. Since I have one with flexible tube I didn't have to touch it, but if you have the stock intake or a PVC/metal intake you might have to pull it off.
Start going after your PB Blaster soaked nuts and bolts. These are all 13MM. I used a shallow socket for the front and deep for the rear. The front two are pretty easy to get to and remove. These are the ones that are least likely to break. I would personally go after them last. The bottom bolt on the rear is where your ~2ft of extensions comes into play. Run the extension under the throttle body/intake piping until you can easily turn it with the breaker bar. Don't be surprised if a bolt snaps here. The top bolt can be accessed with some shorter extensions but is just as likely to snap. You will not have nearly enough turning room here so it will be *click* turn *click* turn etc.
Rear nut for heatshield:
Once you have the two rear nuts off you can pull the heatshield off. There will be two more nuts underneath that are attached to the bolts (as in the bolt and nut are one piece). This is where you will probably need a deep socket to remove them. Don't be afraid to spray some more PB Blaster in there. This is also where I snapped the top bolt on the rear.
After all the nuts and bolts are removed the crossover should just pull right out and the new one should slide right in. You may have to wiggle it and rotate it if you left your intake on. Loosely tighten all 4 bolts until the flanges are all lined up. The front flange has a marking on it to tell you how to install it but the rear did not have any markings. You can use some sealant here if you are afraid of leaks, but the factory system did not use any sealant. Tighten down all 4 bolts, slide the headshield on, and then tighten down the 2 nuts for it. Reinstall your intake if you took it off.