If you used a site template (such as the Document Center template) and wish to use a different template (such as a Team Site), how can you accomplish this? More importantly, how do you do this without losing permissions that have been setup on the document libraries, lists, etc?
Unfortunately it is not possible to change the site template after you create the site. In some cases you can manually change things to make something look like something else, but the underlying site will still be based off of the original site template.
If you chose a Document Center and don't like it and want to switch to a Team Site template you will need to provision a new site and then manually copy the data or find a tool that can migrate the content for you. Some of those migration tools can also move permissions as well.