The cut-out pressure is usually 50-60 psi. You'll want to shut it off at the breaker so it doesn't damage itself.
It should have a grey plastic box that measures about 3 x 3 x 5", with a small acorn nut on top. This is the pressure switch. After shutting off the breaker, take a look inside, the contacts are probably stuck together. You can manually un-stuck it, but it will probably stick again in the near future. You'll want to buy a new one, they aren't to hard to install, but if you have any doubts, have a plumber or electrician install it. Get the Square-D brand, it's the only one I know of that's any good. You might want to add a pressure gauge at the same time if it doesn't already have one.