What's the best way to blur out only a certain part of the screen w/ FCP? For example, I have a shot of a car dealership and I want to blur out the bottom grassy part of the frame to make the text in that area stand out more. Is there any easy way to do this?

You could copy the clip and place the copy on top of original then garbage matte out the grass in the top clip and add a blur to the bottom clip.
doug