Muffler Parts - What is this?
 

I own a 1993 Nissan Sentra Classic (4 Cyl, 1.6L, 4-door). The muffler needs replacing and so MufflerMan quoted me $400 CDN to replace:
Resonator/Pipe Assembly << where/what is this?!
Extension Pipe
Muffler
Exhaust Gasket
Exhaust Gasket #2
Exhaust Clamp
Exhaust Shop Supplies

I would like to explore replacing my muffler myself if possible (never done something like this before). Is there a site that can show me the above parts so that i can match them up with my vehicle?

Thanks.