you're an 02 right?
depends exactly what you want to do here....if all you need to do is to connect the blue plug to the back of the NIT without removing the NIT, then you won't have to remove the whole centre tunnel....
to do that you will need to open the lid of the armrest, unscrew to screws which should be visible straight away...then you will need to lift the rubber mat as well...under there should be another two screws.
Undo all of these, and remove the compartment base...once done you can see inside the armrest. Now....in a coupe you have two air vents facing out of the rear of that armrest, in a spyder i doubt you have...so you might just have empty space....can you see a blue connector down the bottom yet?
If you need to remove the NIT then in addition to the above you will need to the following:
Inside the armrest at the back there should be two screws which basically bolt the rear of the tunnel into the car...undo these.
Then in the cigarette light area, remove the inside box...it just pulls out. Under there, you will see another screw. Remove that...once you remove it, you can pull the cigarett lighter unit out...unclip the connection underneath it.
Once you've done that, you have one more screw to undo. In front of where the cigarette lighter unit is/was, there should be a little open compartment (about the size of a small mobile phone, or an ipod). Underneath the rubber mat there is a screw...undo that one.
Once all of this is done, you will need to unclip the leather glove that fits around the handbrake...you don't need to remove anything, just undo it. This is to allow enough freedom to move the whole tunnel around a bit.
Now that the tunnel is basically undone you can lift it enough to get your hands underneath the NIT. Underneath there, the NIT is bolted in with 4 bolts (one in each corner). These bolts are actually screwing into the NIT from the cross bars underneath. You will need a socket to undo these...unfortunately i can't remembr the exact size. If you have enough space you could use a spanner/open wrench or heavy pliers to get a grip. Undo these 4 bolts, but hold onto them as you unscrew...as they will fall out into the tunnel below, never to be seen again.
Once all undone the NIT will basically pull out (pull to the front and up)...you may want to undo all the connections though if you want the NIT out of the car completely. If you don't and just want to have a look underneath/around the sides...then you can leave all connections in.
The is a heavy duty cable that plugs into the front of the NIT at the bottom...this goes to the display. Be careful not to trap that cable.
Hopefully this all helps.
Reverse procedure to put back.