There are two sections that you can unlock for 20 credits each. Does anyone know if its worth it? I recall the other ones you unlock and win prizes including credits. I have no idea what you win for the locked ones
If you want to complete missions then I would deffinatly unlock them.
Other wise its up to you, as far as i remember you don't completely get the credits back but you get BP and XP and slot machine tickets.
here is the list of missions and prizes. It's fun and I think it's worth it.