Extra gauge to add to pod? Mildly modded '98 GST

[89_Colt_GT]

GTP: The best offer I got for it was $3,500 cash and I couldn't let it go for that, so for now i'm gonna keep it as my damn reliable daily driver.

ok, so with an aftermarket oil pressure gauge, should I disconnect the old sending unit, replace it with a new one, and that way the gauge on my dash won't show a reading, however the aftermarket gauge will.