A woman at work is marrying a Moroccan, he's their national heavyweight champ I think.
Anyway, you can fly directly into Agadir but the flights are less frequent and more expensive than flying to Marrakesh. For the best deals on flights try
Royal Air Maroc.
Some nice 5 star hotels in Marrakesh that are fairly cheap. I'd also reccomend a trip to Safi, a quaint little fishing town.
Top tip is to not eat in the hotel restaurants, the food is kept heated all day and a high chance of food poisoning. Best bet is to eat at the little roadside shacks, even though they look a bit shabby the food is cooked fresh to order and is real authentic Moroccan quisine.