there are several area in the exhaust system that can get worn , muffler, pipes, cat converter, worn exhaust gaskets, anyone of these alone will cause that loud noise comming from underneath. It is always best to have the vehicle looked at by a muffler shop, also most major chains will give you a free inspection, (keeps you off the ground), normally the tech will show you and answer your questions and give you a free estimate (make sure the shop you use does FREE inspections), you are not required to have the work done at that shop, Do price around,look for specials, ask others for references, use local shops coupons, and always ask about warranties most are 90 days. finally this is not a dealership issue most local and major chains can repair this problem. It comes from time and weather/fuel conditions to these parts because they face all types of enviornments. The time to replace say a muffler is not long. Also ask the tech about other work that may need attention at a later date (have them to write it down for you), even though it is best to get the needed work done as soon as possible. Ask the tech to always give you a complete total of cost, a muffler for this vehicle varies.