When I had the intake off my VG30, I did the plugs, cleaned up the casting around the plug holes so dirt/water could escape more easily (the drains into the valley were mostly blocked by casting flash, so there was a lot of junk packed in around the plugs), did the valve cover gaskets, and cleaned out some rodent mess. Look for rodent damage or anything else obviously scabby with the injector harness. Inspect anything rubber that you have to mess with--I don't remember finding much wrong, but your climate may be harder on rubber than mine. Look for cracks, look for coolant residue. If the vacuum lines to the EGR and FPR are original, go ahead and replace those while you're in there. Might be a good time to replace the rubber line between the two fuel rails, or at least check the clamps. Make sure you mark where the distributor was before you pull it out.
If you pull the lower intake, make sure you get the right gaskets. The VG33 lower intake gaskets are thin and made from stamped steel. Make sure you don't get the VG30 gaskets that are thicker steel with rubber seals. (If you get the wrong ones, nothing will line up. I made the opposite mistake and got to take it all apart again.) While the lower intake was off, I relocated the knock sensor to the back of one of the heads. I'm not sure if this was a good idea, but I didn't want to have to dig back down to it if it acted up later.
Make sure you bleed the coolant properly afterwards. Should be a marked bleeder bolt on the intake.
I did my timing belt at the same time--but that's the front of the engine, not the top, and having the top apart didn't make it easier. If anything it just made for a larger jigsaw puzzle.