Hello, i strongly suggest that you look at former alfresco community manager Jeff Potts tutorials. Beside looking at alfresco official documentation wich Contains lots of useful informations about administering and dev on alfresco 5.0, go to ecm-architect.com and start jeff Potts alfresco developper series tutorials. All you need to know to start extending alfresco is there. It has been updated in the early 2015.