You would need Vista to enable DX10 but Acceleration will run just fine in XP.
If you can load the F18, but the gauges are not working, it might be a Simconnect issue. You can try installing the FSX SDK (from FSX DVD 1), then download the latest SDK from fsinsider.com, and install it. Installing the SDK might fix your Simconnect installation.
Also, you can try turning off your firewall. In certain cases, firewalls block Simconnect operations.