help with dysfunctional shower...

My wife and I just bought a house (built 1996), and to our surprise, on the first night, my wife tried to take a shower only to find that only hot water comes out of the shower/tub faucet. It is a Moen single handle shower valve, pull to turn on, and turn to control temperature. If you pull it out and turn it to the left (hot), water just pours out, and gets super hot. If you turn it to the right (cold), it completely shuts off. I am a handy guy, but have little experience with plumbing. Can this be fixed easily? I've heard about replacing a cartridge, but I'm not sure if that is the cause or not. Anyone heard of problem like this? Any help would be appreciated....

It is probably a MoneTrol with a stuck balancing spool. Remove the large trim plate and there should be a large slotted nut on the lower left side of the valve. If so, buy a new balancer because the old one will probably break when you remove it. Unscrew the nut, and the entire unit should come out. If it breaks, then you have to fish the remains out, then install the new piece.