I recommend articles and SPSS implementations from Adrew F. Hayes. He is an expert for moderation, mediation, moderated mediation and mediated moderation models. He programmed a plug in for SPSS called PROCESS, which does practically everything you need for either of the topics mentioned.
Please have a look at his hompage, where you can find the latest version of the PROCESS tool, the according articles and appendices, as well as other articles on this topic, to get a more in depth insight in this field.