A resonator is a kind of "mini-muffler" placed behind the muffler in the exhaust. They were used to dampen a different frequency than the mufflers, thereby making the exhaust note more tolerable. Road Rage can be caused by the exhaust tone of your car. No kidding. There seems to be some range humans don't like.
take it to a garage and tell them. if you want to DYI, just cut the pipe before and after it and put in a piece of straight pipe.
I have a 98 with the 4 cyl and most of the exaust is cheap except the first part which includes the Converter and holes for O2 sensors. I am in Canada and was quoted $800 for this section, and $300 for the rest of the exaust, which includes the intermediate resonater and muffler. I also know that the 6 cyl is ridiculously priced as well