This is what I am going to do: I have a NOWS SBE 2.5.1 Server (SLES 10.3, OES 2.0.3) with GW8.0.3 and I have to upgrade to GW2014. As far as I know, there is no way to achieve this with NOWS SBE.
The only way I can think of is to first migrate GW8 to a new server (SLES 11 with OES 11) and upgrade GW8 to 2014 then.

Unfortunately the size of the GW8-system is larger than the space available. I can't copy GW to a new location. So I have to do that on the same server or mount the old disk to the new server (all servers are VMs (VMware ESXi 5.5)).

I would follow TID 7013085:

1. I use the same server
Then I would remove any replicas the server holds, wipe out the old OS, clean the eDir of all server objects (not the GW objects), install the new SLES (same IP/Servername) and OES, so the new OES hopefully reintegrates into eDir. Then I install GW8. If it runs correctly, I would upgrade to GW2014.
This would be like a fatal server crash (TID 3361110) with reinstalling. I can see the problems installing into eDir now already...

2. I use a new server
I install the new SLES/OES with new name and IP. This integrates perfectly into eDir. I mount the disk of the old server to the new one and follow the TID until I have a working system. Then I would upgrade to GW2014.
My concern is that I install a "second" GW8-system. Isn't that a problem for the eDir? Anyway, I can't install the same server into eDir again, but the same GW8-system is ok? Really?

I would appreciate your thoughts about that.