How would you get a matrix orbital/crystalfontz LCD screen to do things like check your voltage/fan rpms/system temps/etc.?

there is software that you use to set up what is displayed on the LCD screen. Those programs have plugins which allow them to get information from other sources (stocks, news, weather). usually motherboard monitor is where they get the the information you're asking about from.

so the motherboard monitor the temperatures for these things or would I need to invest in some probes?

matrix orbital has a model or two which can read from exteral probes, but i would say it's not necessary if you want to monitor something that has an onboard probe.

just making sure you know - motherboard monitor is a program the gets the information usually from bios - you can download it from the downloads page if you dont have it