Need another question answered, oil guage

[skywarp]

Okay,I have a 98 eclipse spyder GST

I recieved my oil preassure gauge ( Electrical ) , It has 3 wires red, black and green. does the red power wire need to be connected to a power wire that is always powered? or just when i turn the key on?? Instructions doesnt say, actually useless!!!!!.
also cant i just connect the green wire to the current sending unit on the car? Insted of installing another sending unit? They both look the same to me?

any help would be great, ill try to scan the instuctions so you can see, and maybe explain them to me

Thanks Rudy

 

[L2RTSiAWD]

Even if it looks the same I would still use the one supplied with the gauge.