How do I work on my older Whirlpool Dishwasher (Model SHU5004-0)?

The dishes are not coming out complete clean. Since I don't really know much about dishwashers, I figured the best thing I could do first is just to clean the jets and anything else that might get clogged up. However, the manual was not left by the house's previous owners, and considering the age of the dishwasher (15-20 years I would guess), I really don't want to spend too much time on a unit that should probably get replaced. The real question is how do I take it apart without breaking something? The Whirlpool site did not recognize the model number, but the unit is also known as the "Super Scour Supreme."