That's the one..
It isn't really possible to leave it in the "wrong" position, since if you connect up shore power and they have it wired the wrong way around, you'll get the reverse polarity light on the AC panel and you simply switch it over.
Yes, it should be wired up after the breaker and before the sub-circuits, so you can switch on the mains, check if polarity is correct, before you turn on the sub-circuits - but there are some (like this one
) that are designed to go before the breaker.
To the best of my knowledge, the worst that would happen if polarity is wrong is you'll trip the shore power breaker - probably the dockside one. I certainly don't see how anything could get fried.
The most common instance of reverse polarity I've seen is the use of home-made extension leads for shore power connection. Of course, it'd never happen to me...