I am playing Old World Blues DLC and I am stuck on this mission. I need to get one more jukebox file but it's not allowing me to go through the door as I need a key. I've been told I don't need a key and I need to complete a mission with Dr. Klein or something first? I been speaking to him but unable to get any more missions out of him.. What do I do?

Do I need to do the X-13 quest? I hate that damn thing not the best at sneaking.

Any help would be appreciated,

Thanks.