we are contemplating a quantum leap from our current GroupWise 6 system to GroupWise 8.

The specifics are:
2 Post offices geographically remote from each other running GW 6 on a NW5.1 OS. At the head office we are running the GWIA agent and gateway for Webaccess to both sites.

Is it as simple as running the upgrade on the current install or would it not be recommended or would it not work because of the OS level? If not recommended, what might be a suitable upgrade path? (We also have a newer NW 6.5 server at each site in the same tree)

Would we need to upgrade both PO's at the same time or could we perform the update on the Head Office then schedule at a later date the remote site?

I have also read that the GW 8 client will not work on less than Windows XP OS's. If this is correct, is it possible to use a GW 7 client or would we need to upgrade anything pre windows XP to something more recent?