Unitrends has a version of their Enterprise Backup virtual appliance that is free for up to 4 VMs. They also offer a *very* easy to get NFR license that is completely unrestricted and free.
I've P2V'd a few SBS 2003 boxes, and I've found it to be easiest just to cold clone the box and not having to worry about stopping all the services or DSRM or anything like that.
Yeah, it might result in a little more downtime, but you don't have to worry about AD or any of the services...
In the vSphere Web Client, you can right-click on a VM and go to All vCenter Actions -> Compatibility - there is an option called "Schedule VM Compatibility Upgrade" (if the VM is powered on) or "Upgrade VM Compatibility" (if the VM is powered off).
My employer is a Dell reseller, so I have a decent amount of experience procuring and later troubleshooting Dell servers. I've found that they are kinda prickly about supporting 3rd-party hard drives in their servers. YMMV.
If at all possible, I'd order the drives through Dell when ordering the...