I really want to change some small features on my face. The problem is that I am a Vampire Lord in the middle of the Vampire Lord quests. I know Serana can change me back into a Vampire Lord, but I am wondering if I have to finish the Vampire questline in order for her to be able to do that.

not sure if Serana can turn you back into it if you chose the vampire side, i never really thought of curing myself and trying to become a vampire lord again (yes i sided with the vampires as well)

Okay, I figured out that she can change me back in the middle of the quest line. Is there any way to NOT have black lips when I become a vampire?

You might be stuck with that.