[dmforcier]

There is no need to use a multi-meter to change out the switch, unless you are using it to detect any hot wires.

If it's a typical multi-meter, the black lead plugs into the Ground socket and the red lead into the VAC socket. If there's a dial switch on the front set it to some VAC number greater then 120.

Test whether you have it set up correctly by sticking the probes in a live electric socket and read what it says. Analog or digital should read somewhere between 110 and 120. Some analog meters will have multiple scales, so find the right one to read.

Then you can repeat on the switch when you pull it out. I would do it with the breaker on so you can prove to yourself that you're reading the right thing. Then turn the breaker off; you should see that the same reading is now zero.

IMO, it's much easier to use a non-contact voltage detector, but it might not be convenient to acquire one - and not really necessary.