Extra times to consolidate everything, not to implement it; implementing gallery systems is pretty simple if you start off meaning to do that, it's just a matter of calling the scene with the right variables set.
Save systems are simple if you've done the coding right, you just have a save class that every object inherits from, game like this would be pretty simple since you would have to track physics objects, just the current state of whatever they have managing their current quest variables and the player variable. Not that hard to put in. Loading is just loading the save back into the save class and loading the scene using the given data.
More complicated the game the harder it is to put in a save system, this one is linear with no physics objects that need to be tracked so it'd be easy.
