I've had the OSE version installed, then installed the PEUL version on top of that, without uninstalling the OSE. The installation application seemed to do that for me and the PEUL version ran with no ill effects. Did the same with PEUL version to newer PEUL version, also with no issues. As far as I can remember, the only thing I've ever uninstalled with regard to VBox, is the parts of the guest additions that normally come with PCLinuxOS.
The last upgrade of getvirtualbox uninstalled the existing VBox installation, without asking, and without being run, just being installed from Synaptic.
That's been my experience, as well.