installing new temp switch for electric fan?

[diesel driver]

I have an 86 300sdl, My electric fan works in moderation. I bought a new switch which is brass and looks as though it needs to contact the coolant. Is this something I can do myself of should I let my mechanic do it followed by a charge?
Thanks

[stevebfl]

The fan is controlled via two sensors. One is in the AC and will require system discharge and recharge. The coolant temp sensor is into the coolant and is best done cold and quick with the rad cap off. so there is no pressure. A small amount of coolant will be lost.