From Win2003 Server VM to Win2012 - domain controller

Hello Smart People,

I have a client that needs their Win2003 server (DC) migrated Win2012. A plethora of information is available on this process, as most IT folks have probably been embroiled in this process several times during the past 12-14 months. I have one related issue and one follow up question.

Issue

The current win2003 server is running on a VMWare ESXI 4.0.x implementation along with several other VM instances. Room is available on the same guest host to make the Win2012 installation. There are 4 disks allocated to this Win2003 server from the available VMWare storage, including 3 (500 g +) from a internal array and 1 (1.5 tb) from an external QNAP NAS.

So my question / issue: I will need to keep the data from  3 of the 4 disks available to the new Win2012 server instance. Is there way to do this without copying off, recreating and re-populating the disks?

Question

Most all the documents I have reviewed regarding Win2003 DC  > Win2012 refer to several manual steps, include transferring FMSO rules. While this process makes sense, shouldn't we be able to just add the Win2012 to the existing domain (managed by the Win2003 DC) and allow the configuration to propagate? Then we can just demote the old Win2003 and promote the new win2012.  Is this correct or am I missing something.

Thanks much for any guidance or advice.

Stefan