There will be several hundred capacitors in your machine - if one of them has failed and needs to be replaced to solve the problem you have - it might take several hours of fault tracing to track it down - the fault may not acatually be capacitor related - although it may be. A "blind" change all the capacitors approach is not realistic.
The fault you have appears to be heat related i.e. as the machine warms up the fault becomes noticeable.
Such faults can sometimes be induced with the covers off and the careful application of heat from a hair dryer - similarly you can buy freezer-spray from hobby electronic shops to cool down selected components in an attempt to make the fault go away.
Given that you need to ask how to recognise a capacitor I am doubtful that you can achieve a repair on your own - you will need confidence and a soldering iron and a hair dryer as a minimum.
Google has a feature "images" that shows pictures - enter capacitor - there are hundreds of different types and sizes - some are polarized meaning they need to be fitted a certain way round. They all have two terminals.
Wikipedia article here...
http://en.wikipedia.org/wiki/Capacitor
Good luck...
Peccavi
March 2010
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