I need to see all the articles for a given publication in my replication setup. Is there a system stored procedure that lists all a publication's articles?

Yes, if you're using transactional or snapshot replication, you can use the system stored procedure sp_helparticle. You can run this procedure, executed at the Publisher on the publication database, to enumerate information about a specific article or all articles in a publication. If you don't specify the procedure's @article parameter, the procedure lists all the articles for the specified publication. See SQL Server Books Online (BOL) for details about using sp_helparticle. For merge replication, you would use sp_helpmergearticle to retrieve article information.