All of these questions and more were explored in a recent Gizmodo article: How to Survive the Modern Day Breakup. The basic takeaway point from the article is that you should use the same common sense prudence in your online life that you should use in your offline life.
For example, you wouldn't throw away family pictures just because you're getting divorced, but you might put them away in storage for a while. Similarly, you might want to remove your online pictures and save them on a hard drive, CD or DVD that you keep but put away for now.
Another example, is how you should handle relationship status changes. You might now want to call all your friends and tell them you're getting divorced. Similarly, you can change your relationship status on Facebook without having it appear in everyone's news feed by changing the privacy settings for your status.
Finally, consider what you write online to be as public as what you tell your most gossipy friend. If you don't want your comments to make their way back to your ex, then don't tell them to mutual friends, and don't post them online.