As you can see, my dynamic as been posted as part of my signature. Now I'm wondering, will it automatically update itself since it's coming from the hiscores, or will I need to constantly update my dynamic?

Your signature will update automatically once every 12 hours :)

awesoem, thanks.

The only part you have to update yourself is your quest points and that's easy to do without recreating your signature. There's a little guide on how to do it on the signatures page.