1999 Chev 2500 6.0L A/C

[AB Dave]

I am replacing the a/c pump on my truck. There is a sensor, or switch, on the rear of the old pump which is held in place with a snap ring and simply pulls out after the snap ring is removed. The new pump has a plug in that location which is also held in place with a snap ring.

Is it a sensor or a switch? Do I need to install it on the new pump, or is it something the a/c system can do without? How many cans of fluid will I need to refill the system?