Almost any part of your exhaust system can be replaced independantly - If you want to spend enough time and effort and if you are lucky. Some parts are easier to replace than others.

If the part that is bad looks difficult to replace, you should have the rest of the system examined carefully. The most expensive part is usually the catalytic converter. Often this part does not need repair, and the system is replaced with a "cat-back system"

Often you can get a decent price on a kit that includes the entire cat-back system - all new parts allows you to cut the old system off and work with all new pieces during assembly.

This saves you a great deal of labor and reduces the risk that the repair goes wrong or does not last.
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3 8s & 2 7s 740,000 miles total

Nope, it's not necessary to replace the muffler, just the tip

http://shop.ivalueinternet.com/bigexhaust/index.cfm/action/home.htm

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Dennis