I've done a few uppipe installs, so here's my advice ...
If none of you have done an uppipe install, plan on an afternoon install (that could go into the evening).
Beer (and plenty of it). Figure 6-8 beers/each for a moderate drinker (more if you guys can chug them down). This may slow down the install process, but it's worth it. Also, make sure you have enough food in the house to feed your friends, or be prepared to order a pizza or something. These two are the most important parts of the install.
Get new hardware (bolts, nuts, studs) ahead of time just in case - even if you don't end up using them, it's relatively inexpensive as a "just in case". Get a bolt to plug the EGT bung (the EGT is placed there to monitor cat healthiness, and since you don't have one anymore, you shouldn't reinstall it), and a resistor for the "EGT fix" as well.
Replace all gaskets. The minimum gaskets you'll need are uppipe/manifold, uppipe/turbo, turbo/downpipe. If you've got a 3" flat-flange downpipe/catback gasket and aren't going to drop the whole TBE, pick another one of those up as well. Depending on your install approach, you may need exhaust manifold gaskets as well (determine this by what install directions you decide to follow).
Make sure you have Internet access handy. Print instructions beforehand, but being able to find a second (or third) set may prove useful.
The older your vehicle is, the more important something like PB Blaster will be. Spray all nuts/bolts liberally before even attempting to break them free. After spraying the bolts, it's a perfect time to drink a beer or two and BS while you let it "sink in".
Lastly, have fun with it. You'll end up with busted fingers/knuckles, and use plenty of expletives, but in the end, you'll be proud of yourself that you were able to complete a relatively DIY mod.