In 5.1 you can export and import the configuration settings listed here, but you will be unable to do that in your case.
VDS Export/Import with PowerCLI | VMware PowerCLI Blog - VMware Blogs
It appears you are trying to do thsi in a 5.x environment though. You will have to move all your hosts to a standard switch and then unregister/reregister at new Vcenter.
The process is well documented on this blog posting:
http://virtualkenneth.com/2012/10/19/migrate-to-new-vcenter-server-while-using-dvswitches/