Windows Server 2008R2 convert basic disk to dynamic questions

I need to expand a volume on a Windows Server 2008R2 virtual machine, due to the limitation on virtual disk size imposed by the underlying virtualization system. I have come to understand that I need to convert the current volume to a dynamic disk. So I have a few questions.

1. can it be done online?
2. is it safe?
3. what risks are involved with converting a basic disk to dynamic?

I've been googling for over an hour, and have found precious few answers to these questions, none of which have been particularly helpful.