The trip is definitely not for trekking beginners. I will recommend some reasonable training before attempting this trek, and you must have really comfortable and broken in trekking shoes! Blisters galore on this trek compared to numerous treks in nepal.
I went with hunza guides, (can search on the net), and my contact person is Amir. Highly recommended, but i don't know whether they are competively priced, as I did a mountaineering trip with them, not a trekking trip.
Please feel free to feedback any additional queries to me.