1. Nismo one is a direct fit, but the Bosch 044 is pretty darn simple to install.. A couple of cable ties or clamps, attach the sock filter, wire it up and voila. It's a lot cheaper too and is interchangable between your GTRs... For some reason the NISMO catalog lists different part numbers for fuel pumps for R32/R33/R34 GTR...
2. If you want one that's interchangeable, just buy a generic kit from either HKS or GREX... They'll bolt on and mount in front of the radiator on the driver's side... The car specific kits aren't interchangeable as they sit in the passenger air duct and come with air guides and funky stuff but need cutting and fitting.
3. I've got the GReddy 600x300x115 sitting here waiting to go on as well... Seems like an excellent intercooler for the money, but being 4.5 inches thick, you have to cut away a bit of the bumper to create the physical room needed to mount the monster... I'm not sure what thickness you can go upto without cutting your front bumper.
4. Oil catch can is an Oil catch can. Get which ever you think is the nicest, make sure it's packed with a bit of steel wool.
5. Not too sure on this one. I have ordered HKS ones, but was considering the CES ones. They look VERY well made and designed but are just as expensive as all the Japanese ones. The reason I went with HKS is because I have HKS turbos and HKS front pipes and I *KNOW* that I'll have absolutely zero issues with fitment, whereas the custom-ish CES ones looked........ iffy.