i dont know what to call it but it is the driver side rear fender? quarter panel?just right above the wheels. i need a new one becuase it is heavily dented. should i try to find one to buy? and where would i find one? or should i just get it pulled out and repainted?

 

It is commonly called a Quarter panel. The skin is available from Mazda. A used one will work. Lots of welding and fitting involved

 

That sucks. Go to a body shop and get an extimate. They will tell you if its better to repair the one you have or replace it. The tough thing about quarterpanels is that you gotta cut it at the pillar, weld it on, and then paint to match. Sometimes its just better to repair the damaged one, depending on the amount of damage.
good luck.