Then the sketchup exporter:
http://www.kerkythea.net/joomla/index.php?option=com_remository&Itemid=42&func=fileinfo&id=60

Then get and install some materials and components for both Sketchup and Kerkythea:
http://www.sketchup.com/index.php?id=56
http://www.kerkythea.net/joomla/index.php?option=com_remository&Itemid=42&func=select&id=3

To learn Kerkythea, start with the FAQ's:
http://www.kerkythea.net/joomla/index.php?option=com_easyfaq&Itemid=41

Then check out the .pdf tutorials:
http://www.kerkythea.net/joomla/index.php?option=com_remository&Itemid=42&func=select&id=6

And if all else fails join up on the forums and ask some questions...
http://www.kerkythea.net/joomla/index.php?option=com_wrapper&Itemid=76

Here are some examples of what can be done with sketchup and kerkythea, these are not mine. they are all 3d models, with different maretials and reflections and lighting applied to them, keep in mind, that just the rendering time on some of these may be several hours.