Low pressure switch replacement

[Delorean17@xxxx]

Hi,
I ordered a new AC low pressure switch as I think mine may be defective. 
How is this replaced? Does it just unscrew? Is there a valve that keeps 
freon from leaking out when I remove it?
If this doesn't solve my cycling problem I will have some more freon 
added. It was tested for leaks and none were found but they were not sure 
how much freon to put in the system.

Thanks
David