Factory service manual and a good set of tools. There is a free one online: http://www.300zx-twinturbo.com/cgi-bin/manual.cgi
No, you will die.
It's almost impossible without removing the engine, unfortunately.
my 1990 300zx is idling rough what could cause this?
A 1990 300zx headlight is recessed into the bumper. To remove it, first loosen the headlight bracket bolts. Unplug the lights and push the housing outward. Be careful not to ruin the weather stripping for the lights.
Attached to the middle of the engine block right underneath the lower intake plenum, roughly half way between the heads.
there is none
A Nissan 300ZX? No
Yes.
The "1990 Nissan 300ZX" was a very popular model in it's time. The "Card ID" website noted the carrying capacity of the "300ZX" was noted to be a hefty 1500 pounds.
Remove the interioer trim and you will find two nuts to remove and the whole window trim and all will come out as you break the seal of the black gooie stuff.
The 1990 Nissan interior panels are held in place with eight retaining clips. Pry outward on each retaining clip to remove the interior door panels.
The cabin filter on a 1990 Nissan 300ZX is located behind the glove compartment. To access it, you need to remove the glove compartment by unscrewing the screws and gently lowering it down. The filter is situated in a housing that can be pulled out for replacement. Remember to consult your vehicle's manual for specific instructions and details.