For gaskets oem are the only way to go. If you use the black onyx ones there is a good chance that you will be doing them again in the not so distant future. As far as special tool you will need either a 2" long t-40 or t-45 socket to take out the injectors. A t-30 to remove the high pressure oil rails. A 10mm allen socket to remove the standpipes and if you get new standpipes and dummy plugs you will need a 12mm allen socket to install the new ones. To remove the injector harnesses from the rocker boxes you will need a 18mm 6pt socket to use to squeeze the tabs in. When disconnecting the injector connectors push in on the wire retainers instead of pulling them out and having one go flying on you. And for installing the studs you will need an 11/16 12 pt socket for the stud nuts. When you get to taking the rockers off, loosen up the head bolts that go through them and then remove the 10mm bolts that hold the rockers to the rocker boxes. If you do it the other way around you will bend or break stuff. Keep all of the valvetrain and pushrods in order. Make sure you have the crank pulley with the dowel at the 6 o'clock position before you start assembling. Then after you get both heads on and the valvetrain assembled crank the motor over by hand 3 or 4 complete crankshaft revolutions to make sure that nothing is binding. I have seen a bunch of people bending pushrods on here and I'm not sure what they're doing to cause that when they reassemble the engine.
Any other questions just holler.