if your local stereo shop does speakers, then chances are they do sound proofing.
this term is referred to as:
sound proofing, sound deadening, dyna-matting, vibration reducing, etc etc etc...
i would suggest getting your material on ebay and either doing it yourself (which is fairly easy), or getting the material on ebay and then having someone else do it.
either way the material on ebay is cheaper than what you will ever find in stores.
this material is referred to as:
dynamat, fat mat, b-quiet.....etc etc etc.
you can learn how to do this yourself by going here:
http://www.ehow.com/how_11208_sound-deaden-car.html
and then to learn how to remove all the components you need, you can go here:
Radio, Door Panel, Rear Deck & Tweeter removal for CE, LE, SE & XLE DIY; 56k Beware