1. Is "putting into play engaged with" and "engaging" two seperate things? I've been playing yes. An example of how I've been using this is to use "put into play engaged with you effects" to get around nasty engagement effects (Dunedain Hunter good for this).

2. Can Gandalf staff cancel a shadow effect after its been revealed? I've been playing no, since that would require a response, not an action. Be nice if it did though.

Am I correct on both counts?

1. No, they are the same. There was a ruling in the FAQ that said you can trigger Sam's ability on an enemy that was put into play engaged with you.

2. You are correct. You must discard the card before it is revealed.