Before you call a plumber (I am one), you could learn a little about plumbing maintenance and save yourself some real $$$. The key to any plumbing is a little bit of investigation. But before you start anything, there are a number of real good books by black and decker on plumbing repair. They will take you through small jobs, like this one, in a step by step manner. Most faucet repairs can be done by a savvy homeowner with just a few good tools. A stuck mixing valve can be as simple as a little packing grease or replacing the washer on the inside. The first step is always to turn off the water and do a little investigation. Every plumbing fixture comes apart. So there is always a few screws and cap nuts holding things together. Most of the time the screws are hidden below chrome covers or tops. So look carefully. See if you can find a name on the faucet and talk to your local hardware store man. Many times they can be real helpfull about your particular faucet.