You can do it yourself if you're comfortable with that sort of thing.
If you're paying for the Sprint protection plan, I think they will do an in-store screen replacement for free (if they have the necessary harware). You might want to call around to a few stores in your area before you go in. They only charge the $100 deductable when they have to send your phone off to be repaired or replace the whole phone through the insurance.
I don't know how much it cost, but there are usually smartphone repair shop in most cities. Just do your research before you go in to try to make sure they do good work. And ask about their policy if they can't fix it / break something else.