if i by an ES oval (2 1/4 inches), do i have to get the piping and resonator done at a muffler shop? how much would this cost?

 

Unless you want to piece together bends from Summit or something and can weld you will more than likely be visiting the local muffler shop. The price will vary due to the size and whether its crush bent or mandrel bent. For piping from cat to to muffler and 2 1/4" my guess would be anywhere from $90-up with resonator depending on shop and labor.