Chrysler Repair: Chrysler 300m overheating bad, coolant leak, chrysler 300m

Question
My 1999 Chrysler 300m started overheating and I immediately brought it in to a mechanic(not the dealership) to get it checked out.  They told me it wasn't the water pump leaking it was something else that was leaking onto the water pump and that I'd need to bring it to the dealer.  They filled my coolant reservoir up before they gave it back to me.  Since it was a busy week in Air force I didn't have they time to get the car in right away, so I kept driving it everyday to make the short drive to work.  I found that if I left the heater on it would keep it cool long enough to get me to base, but after a few days of this the heater stopped blowing heat and the car would begin to overheat.  I would stop once it got to hot so it could cool off.  I opened the hood and noticed the coolant was bubbling from the overflow tank and it was brown in color.  My fans are running just fine, also I noticed it doesn't overheat unless I'm moving.  Or better to say, the faster I go the faster it overheats. I ran it to the point where it hits the halfway mark on my thermostat gauge, stopped, let it sit idle, and it took a while before it started to overheat.  But when I'm driving it will overheat right away(less than 4 miles of driving).  Also now that I did that ritual for a while there is a strange noise on the inside of the car.  I thought it was coming from under the hood but I can't really hear it with the hood open only on the inside of the car.  It sounds like a metallic hissing that sounds like the belts spinning almost, because the faster I drive it the faster the ticking (hissing) sounds and when the car shifts gear the ticking slows down.  I'm guessing my only problem at first was just the coolant leak.  But now I fear I may have damaged it really bad.  Wondering if you have any ideas what could be the problem and what I'll need to do to fix it.  

Answer
Ryan,
You cannot run a car without sufficient water and not expect damage to be done. STOP! If you are going to use the car you must put water in the radiator AND half-way fill the overflow bottle or you can destroy the engine. Fill the radiator everytime you go to drive the car until you get it fixed. This is URGENT.
I can't suggest to you what is damaged, but at least do this until you can go to a good shop.
Roland