NWIP Forwarding

We have a WAN consisting of 5 NetWare 4.11 servers. We have just been told that one of our buildings is going to have its network upgraded which means that IPX traffic will not be allowed to propagate across the WAN. They have said that we either have to upgrade to NetWare 5 or enable NWIP forwarding to enable IP communication. As our plan of rolling out NW5 will take some time to complete the second option is more realistic.

How do I go about enabling NWIP forwarding and what impact will this have on our network/server? Will we need to make any changes on the client workstations??