water pump replacement?

Please advise,I have a 1992 topaz,and when idling at light,or in park the car is making a rattling racket.at first i thought it sounded like a loose flap on exhaust but after listening closer it sounds like a worn waterpump.at least thats where the sound is eminating from.It is a very loud clanging sound..could this be a waterpump going,and if so whats involved with changing it out?..Any advice would be appreciated

Probably the harmonic balancer. Grab the belt by the alternator and see if you can move it, if it moves then it is bad.