OK so how does one go about replacing the dash lights , speedo, tach, gauges,ouch

If none are working, them its likely the dash light dimmer or rheostat, that's what it was on my car that adjusts the dash light brightness. If it's a 70-73 I don't know how the bulbs come out for sure but it's likely the same or similar as the 74-78 I pulled the panel in the center of the dash out where the map light is, pretty easy, four screws. For the first three little gauges I think it's actually easier to drop them down. There are weird straps that hold the gauges in place one little screw on edge of the opening will unhook the strap and allow the gauge to drop down. There black sockets on the back of each gauge that just twist and pull out. And that's the light socket. You can also just reach behind the gauge and pull the socket out that way but with only screw holding it in place I think it's easier to just pull it down. I would test one of the sockets for power before I replaced them though. You should be able to reach the back of the tach from this same area after moving some crap around. I really don't know about the speedo I pulled the vent by the driver door out a crammed my hand threw there but I'm also double jointed. Hope you were able to follow all that I have a 260z which has the same dash as a 280z but the 240 is a little.

Also go here

XenonS30

and download the manual specific to your year of Z the original FSM is awesome for this kind of stuff.

Edited October 1, 201410 yr by 2sixTZombii

Having a 73 & a 74, I can tell you that the center gauges are easier to remove in a 74 & later (provided you don't have AC). The FSM has directions on removing gauges. When all else fails, RTFM.

if you replace even one bulb - get a full set and replace them all while you're in there. it's not a particularly complicated job, just a pita and if one is out, the others are on their way...

also, you can get brighter (slightly higher wattage/output) replacement lamps which help a great deal. some folks have also painted the inside of the gauge cans white to add a little more reflectivity which seems to make the light a little brighter and more evenly distributed (bunch of threads here to search).

plan on an afternoon mucking around with it, then be done with it for another 20 years

In my car the one of the wires to the rheostat was loose, which when fixed, made a few work. Then I had to pull them all out and clean the sockets with contact cleaner, they still work now, but all but my new volt meter are still too dim for my liking.