[Via Rob] Dave McKinstry has recently posted about his Approach to Process Customization with TFS. While I have been practising my work item definitions on a scratch project inside a team system VPC before applying them to the production box, he lays out a good process to help you avoid mistakes.
Now if only there was a nice tool that followed this workflow but did all the global search / replaces for you. Another project for the back-burner me thinks.
I found this link on the MSDN regarding Process Template editors and other download links for VSTS extension development. Hope it helps...
H
http://msdn.microsoft.com/vstudio/teamsystem/downloads/