How to customise infowindow?

Hi I’d like to be able to customise the appearance of the infowindow which appears when you click a marker. I have a custom look I’d like to implement but unsure how to go about doing this with this plugin. Could anyone help?

What files should I be looking for to make these changes? Any tips would be appreciated.

I also need to add/remove content from each of these windows. For example, I don’t want to display long/lat values but Instead i’d like to load in a different image for each marker that will appear within the infowindow.

http://wordpress.org/extend/plugins/comprehensive-google-map-plugin/