The P18e is just a model number. This laptop has different names depending where you are in the world, Ranger, 17, 17R1, M17X R5 all have P18e stamped on bottom cover.
The motherboard on these has LVDS and EDP connectors
If the current screen is LVDS then its 60hz
You could buy 120hz screen and EDP cable, that might (or might not work) with Quadro card.
@Mogrules named the correct EDP cable here
https://www.nbrchive.net/xfa/alienware-17-and-m17x.1079/120Hz 3D Screen upgrade for Alienware 17 R1/