From what I have observed. The level does not really change between cold and hot cycles. What does this mean? Also, if it is the gauge itself, how difficult/expensive would it be to replace? Thanks for the help guys.

 

If the level does not change, it could be due to air in the system. Air compresses while water (coolant) does not. Air being in the system will compress as the coolant heats up and expands.

As far as the gauge sender, it is not difficult to replace, but you will need to drain the coolant level as the sensor is located in the side of the driver side cylinder head.