The moderators will do it when they see the post. I haven't submitted a link in a really long time, but I don't think the submitter can change it. Makes sense to reserve it for the mods, given the implications of a regular user swapping out the link of a highly visible post.
Admins (dang, for example) will occasionally notice a request like this and make the change.
great. thanks for sharing.
one e-mails the moderators (contact link in the footer) and asks them to do it.