I am trying to replace a shower only on/off valve however am having trouble with how to remove the medal part that attached to the water, hot and cold inlets. How does one remove this to replace??

So you plan to do a total replacement, right? The valves are either sweated onto copper pipes or threaded intoi copper or galvanized. Can you see threads right at the two connections of no you see a bit of gray solder?

Yes, I was going to but can not seem to understand how that piece was screwed in three places in those pipes. May have to break down and call someone since my water has not been turned off for 24 hours.

Are the screwed in pipe rigid copper or galvanized? If copper they were screwed in and then the copper pipe was seated onto the fitting. To remove a sewat fitting you must shut off your main and drain the system to the point where there is no water present at the valve or sitting in the pipe.