Yep, take it to the radio shop and they will do it.  But if you don't want to do that, then slide the radio out of the tray.  On the top of the radio there is probably some silver tape or something covering a round hole or two.  One of those will have an adjustment knob under it that you can adjust with with a flat head screw driver.  Not sure which way you go for louder/softer, but just use the trial and error method.

Thanks guys,
Five minutes and a screwdriver and all is good.

Joe