CSS styled google info box/window

I need correct code written for a Google map info box/window. I have the code already for a styled Google map but the info box/window is the default design. The window needs to be styled with CSS according to the style I want. It is using a script form Google fusion tables to call up data (images and words) so you need to understand how you write the CSS with that code. I want two actions written in the code. css element:hover so that the marker will change on rollover. The click action to open the box is already written. You just need to make sure it works with the hover correctly. I will need all code commented on and simple instructions to explain what does what. This should be a very easy, quick project if you have the right skills.