I need help with Raul's quest, or tell me if I'm screwed. I killed the Sterling guy to get his gun, and I've already done Arcade's quest. I've had Raul as a companion more than anyone else in the game, but also other problem I can't get back into the Remnant bunker where they all meet up. Its locked ARRRRG!!! Any way I can do this without having to revert to a previous save?

No, Sterling is necessary for the quest. Arcade's quest does not matter to the completion of Old School Ghoul in any way.

Unfortunately if you want to finish Raul's quest then you will need to reload a previous save.

It does matter about arcade's quest because I need to talk to the Doc from Jacobs town right? He's part of the Remnant and I can't get back in that room they meet in. None the less, I feared the worst that Sterling is a necessary speech trigger... :ermm:

You don't need to talk to Doctor Henry for this quest. The three people you have to talk to for Old School Ghoul are Corporal Sterling, Ranger Andy and Loyal.

Doctor Henry is needed for arcades quest. Going through fallout, make sure not to kill anyone that's nice to you they might have a quest for you.

Cheers