Leave as little fuel in your tank as possible, I had a horrible siphoning problem which wouldn't stop during the duration of my injector change. To clear your fuel lines, remove the f/p fuse & start the car, this will remove the pressure. You may consider changing your fuel filter while you're at it, it's actually pretty easy. In retrospect I should have left the fuel filter fitting apart & put a bucket down there, it would have prevented that irritating siphoning problem.
I simple green'd the entire top of my engine & then sprayed off with a hose to make a nice clean work area, otherwise all kinds of crap will fall through the little injector holes.
I didn't use lubricant on the o-rings, just good old engine oil.
As long as you have the plenum off, consider changing the intake manifold gasket if it's leaking, you're halfway there already.
The vacuum hoses break easily, be very careful with them. Also, my fresh air tube from the passenger valve cover to the throttle body crumbled in my hands, it was so old and brittle. New ones are actually still available from the dealer.
Those little circlips that hold the fuel injectors in break if you even look at them. You don't really need them, but if you're paranoid about the fuel injector flying out of the rail, you may consider ordering some spares. Two of mine broke, but the fuel rail holds in the injector just fine.
As long as you have the intake apart, might as well change all the gaskets, they're right there anyways. Consider changing out the distributor cap & rotor, spark plugs & wires, & check the egr valve with a vacuum pump. I went the extra step of replacing the diaphragm on the fuel pressure regulator, you'll have the fuel rails apart anyway.
When you're reassembling, make sure you get all the little vacuum hoses, you'll know if you missed any by the startling hissing sound the engine makes when you start up the car.
You'll need more than one T40 (I think that's the size) bit, I broke two of them just disassembling and reassembling. Get the one that is all one piece, not the two-piece one which is worthless and will fall apart, cheap crap. You'll need a long extension because two of the intake bolts are on opposing sides, easy to reach with the long extension.
Make sure you tighten all the bolts to spec, and come back later on and tighten them all again, maybe a week later, because they work loose! Some of mine could be turned with your fingers a week later, they were so loose.
Good luck, I did this all in one day & I'm all thumbs, so anyone else should be able to do it too.