Hi Simon,
You have the HttpMonitor template - there at the left (sorry - not on the popup menus from the bottom but under Monitoring Templates). If you go to Graphs (3rd down in that menu) then you should see values for time and size, provided your Zenoss server can actually get access to the target device.
I am intrigued that you have managed to install the PrinterNMS zenpack - I wouldn't expect it to install anything with py2.6 in its name and it did horrible things to my Zenoss when I tried to recompile it for Python 2.7. Can you still get to see the INFRASTRUCTURE menu??
If, as zenoss user, you do zenpacks --list
do you see ZenPacks.TwoNMS.PrinterMIB in the list?
Re starting afresh - it depends why you are doing this. At present, there isn't support for Debian for Zenoss 4.x - expected soon, but "soon" seems to be a long time coming 
. If you areally doing a proof-of-concept, then I would hang in there a bit longer with your VM and winkle out some of your issues first.
Cheers,
Jane