A/c switch. I am trying to find out how to replace the high pressure switch in my, RUUD central

Question

I am trying to find out how to replace the high pressure switch in my, RUUD central A/C unit. The system is empty, as the high pressure switch was leaking.I am having trouble where the copper line, on the switch, goes into the high side line. I can see it is not soldered.Do you need some kind of special tool and if so how and where I can buy one.
Thank's for your HELP!!!!