Exchange 5.5 Outlook Web Access

We do have 6 Exchange Servers 5.5 SP3 and Outlook Web Access (OWA) is installed on one of the IIS servers 4.0(Server Name: TP100TS). This IIS server is pointing to one of the Exchange servers (Server Name: TP03G) for exchange directory information. We are planning to decommission this Exchange server (TP03G). I want to change the Exchange server name (TP03G to TP17G) in Outlook Web Access server (TP100TS). Can you please advice me how to proceed with this change.