If you go into Accounts prefpane in the System Preferences and delete an account from there, it will give you three options.
1. Save the home folder in a disk image. (Self explanatory)
2. Don't change the home folder. (The account is deleted, but the Home folder stays untouched for you to delete at a later time if you want)
3. Delete the Home folder. (Deletes the account and the Home folder)
In order to save your bookmarks/topsites/saved passwords in Safari, just backup the ~/Library/Safari folder from the old account, and restore the items in that folder to your new account.