Thanks for responding.
My problem is there isn't an MXD to begin with. Using Python I'm creating a geoprocessing service (using arcpy.CreateGPSDDraft) that has a result map service tied to it. Since you can't set any metadata for a result map service when you create it, I was hoping to add it in after. The Title was an important one since our application reads this in for display to the end-user. If it can't find the title then it displays the service name, so we ended up making the service name a bit more readable (which is difficult to do when you can't use spaces).