Subtitled as the first extension for Alhambra, "Die Gunst des Wesirs" is as a matter of fact a collection of four separate extensions which can be mixed with the base game in any combination.
The primary module is "Die Gunst des Wesirs" which allows players to play a round out of turn. The penalty for that is of course skipping a regular turn.
"Die Bauhütte" introduces a number of new tiles that only count in the scoring when other tiles of the same color are built next to them. Bauhütte tiles are free, but their number is limited to three per player.
With the "Wechselstube", players can buy building tiles by mixing different currencies.
The fourth module is a set of bonus cards that are placed in the money pile. Each of the tiles shows a particular building. If that building is part of your Alhambra, then the bonus card will count as another building of that category.
Owners of the first edition of the game (titled only "Alhambra") will notice that the color scheme of the "Wechselstube" does not agree with their currency cards: later editions of the game had differently colored currency cards which can be more easily distinguished from each other.