How should I prepare for it?

don't think about it as the job you really want..think of it like you are the person they've been looking for all along. sell yourself by being confident in your abilities and being personable. i know it's much harder to do, but knowing that you are more than capable of doing the job is important, but don't come off as arrogant.

Is there anything I should bring? Should I bring a copy of my cover letter/resume even though I submitted them already?

yes, you should always bring copies of items you have already submitted. don't forget to bring your references as well.

if they like you, they'll ask you about salary/wages. don't give them a number. make them work for it. ask them what they typical rate is for the position for someone with your level of experience. you don't want to short-change yourself, and if the pay is less than what you are looking for, it opens it up for negotiation.

good luck