Right, the v6 is a different engine to the op's and is significantly more difficult to work on. I would argue that this is a specialist only engine unless your confident about the garage in questions ability to fix it.
As for the flood causing the tensioner to fail that is highly unlikely. The main reason the belts fail on v6's is the tensioner fails and causes the belt to rub against the covers until it snaps.
They do this of their own accord, not because theyve gotten a little damp 6 months previously.