Hi,
I setup my build definition, is that all I do when it comes to setting up my build using the Team Explorer GUI?
It seems like the only thing for me to do now is edit the msbuild .proj file?
Is there a GUI for this or its all hand editing from here on it?
Currently there is no MSBuild editor inside Visual studio, but I've read that there gonna be one in Visual Studio Team System 2010 (one based on Workflow Foundation renderer).
If you really want a GUI you could try Microsoft Build Sidekick v2 but it is not free (55$) and not very useful in my opinion.
In TFS 2008 some of the information about a build can be edited through the GUI, but not much. If you right click on the build definition and choose Edit Build Definition you can change the workspace mappings, retention policy, drop location, and triggers. To change anything else you need to edit the .proj file.
What is it that you're trying to do? If you ask a specific question you might get interesting answers.