If you're the type of person who was worried when NASA crashed their lunar orbiter into the moon because you thought it might knock the moon out of orbit then this scenario should be a real nail biter for you. I know it is for me...
What is a gravity assist? http://en.wikipedia.org/wiki/Gravity_assist.
Update: Apparently I put this comic up a bit early, IE before it was really done, so I guess I'll have a revised version up 03/24/09 in the evening.
Update II: Uploaded revised version 3/25/09 12:36AM. Last update almost accurate.