Is there a way I can shift all events in my Google Calendar, +/- a week?
There's no way to do this through the Google Calendar web app since it's built for interacting with one event at a time. See:
You might be able to accomplish this using a third-party client such as Thunderbird or Outlook.
Of course, if you wanted to you could write a script to do this for you. Remember to use some kind of date module to do the "add a week" feature, since adding a week to a calendar date can get very tricky. See the Calendar Data API: