Smoke20,
Humminbird PC is just an application for your computer to manage waypoints. So, yes, go ahead and install it. Son2xtf is another PC application that will convert your sonar recordings to xtf format so they can viewed by some 3rd party viewers. Probably not needed.
As for updating your unit, first you need to know what the current software version on it is.
You can do this by powering on the unit and hit menu when the startup screen appears. Then scroll down to System Status and you will be able to see the Software Version thats installed.
If it does not show 4.970, then you will need to do the update.
Hope that helps,
Robert