05 Sentra Aftermarket Temp Gauge

My temp gauge does not work. Yes, I am sure it's the gauge, not the sender, not the heads, not the coolant....When you turn the key on, the gauge pegs and sometimes if you hit the dash just right, the gauge will come back down.

I want to install an aftermarket gauge and was wondering if anyone has done this? Is it a difficult process or easy to do? Any problems with doing it?

Thanks