The SvcTraceViewer, if configured correctly, can give you both the activities take place during a service call and the message body itself. Using the config in the here, you only get the activities. Here is the configuration if you want both the activities and the message body:
The initializeData attribute on the sharedListener node will define the log file that you want to create with the trace information. Then you are ready to run your trace. For my set up, after I run, I see an Accounts.svclog file appear in the root directory of the application. This file can then be opened by the SvcTraceViewer.exe and analysed:
If you see the 'Received a message over a channel' and 'Received a reply over request channel' then your config is correct. Now its time to figure out if the message coming back is correct!