I want to be able to add the resolution field for all Service Requests so that when customers view items from the Self Service portal they know what was done. I can find the the business object to edit for incidents but not for service requests, does any one have any ideas?
You are limited by what you can do in Self Service, but what you can do is create a custom form in the Service Request BO and display that form on the 'Service Request Progress' tab, here's one I created previously to display the Approval Status, Tasks Status as well as notes/attachments:
You could easily do something similar that includes the Resolution field.
Once you have your form, you modify the My Items workspace in the Self Service role and point it to the newly created form: