the serial number is on the rear of the unit. if it has the cable cover on, it will be obscuring it - so just get him to pop it off. It will also be obscured if the unit is in the wall bracket.
No huge problems with Ouvertures. Check the Tape Mechanism hasn't siezed through lack of use, and try to buy a 'straight laser' as opposed to the curved laser - they are more reliable.
The straight laser tracks straight up and down at the 6 o'clock position, and the curved laser tracks in an arc at around the 7 o'clock position. You can see this just by looking at the front of the unit.
Hope this helps, and welcome to BeoWorld! 
Lee
BeoWorld - Everything Bang & Olufsen