Then again you can never be too careful. My cousin got his identity stolen and it was after his computer was in for repairs (it happened shortly after that). It might of been a coincidence, but they never caught the guy and it took 2 years before his credit was restored. You just never know who will be working on it. I hope Apple has some security measures in place for this, but don't they send it out to others sometimes?
Back-up your stuff and make sure you delete anything important like CC numbers, addresses, phone numbers, ect..