Installing aftermaket Tach

[undertow29]

Really quick question for all you smart yoda ppl...

I am installing a aftermarket tach on my 90 22re 4x4 manual. And first i wanted to know if anyone knew the color of wire i should tap into off the steering wheel to get my illiumaition when i turn on my dash lights or park lights/head lights...

And secondly next to the fuse box (under the hood next to the barttery) there is that little box labeled Diaogsis and between that and the fuse box is this little covor that says ig- now that is where i plug the tach in correct? then i run a wire to my illuimaiton? And i find a hot wire? Any suggestions on what hot wire to use? or is it best just to run a fused line off my battery? I kinda wanna avoid any extra wires under the hood.. I can proved pics if its easier then my poor explation..