Your assumptions are correct,but there is a bug issue. you will have to reload a saved game.
The key is to make sure you dont pull the lever till each statue is lined up. once a statue is lined up,use that lever.
The bug comes into play,because the statues reset every so often,just need to time it so that you dont pull the lever unless they are lined up.
Yes its worth it,you get some decent items,but it varies. If you miss it,it isnt that big of a deal either.
PS: the best item you can get early on is the sword esseric,and it can be in several formats. By using dialogue you can make it into a longsword,shortsword or bastard sword.