For vCloud I would recommend this: http://www.vmware.com/files/pdf/VMware-Architecting-vCloud-WP.pdf
But are you sure your company really needs a cloud? You mentioned your server room is small with only 4 servers offering some basic services.
But virtualization is no doubt the way to go if you want to reduce costs and consolidate your physical servers. As regards storage it's difficult to say how much space you would need, but judging by the size of you server room maybe not much.
Take a look at VMware's Virtual SAN solution, it allows you to virtualize even the storage part of your infrastructure, thus eliminating even the NAS. https://communities.vmware.com/servlet/JiveServlet/downloadBody/25933-102-2-34324/VMware_Virtual_SAN_Whats_New.pdf
Also, there is really a lot to learn before implementing a virtual infrastructure. Not to mention one needs to have at least some experience administering virtual environments to efficiently and correctly design and implement a vSphere-based infrastructure. As grasshopper suggested, I would strongly recommend taking a course to learn the basics of vSphere.