Convert existing WordPress site to membership site

I have an existing WordPress website that I wish to convert to a membership club sides using the various WordPress plug-ins and retaining all the original design etc. Members will be able to purchase downloads of MP3s various personal development. Stress management articles as well as e-book's and courses using the automatic responder, once the site has been completed. It is essential all updating work can be done in-house the bidder must be experienced in WordPress membership sites, and I would like to see a portfolio of previous work for any further information please contact me. Kind regards, David Briscombe