1. I would follow Yooper's advice here: http://www.homebrewtalk.com/f13/how-...-fruit-281866/
2. Yes, fruit clogs everything up in my experience, I ended up racking with a paint strainer over my racking cane and my brew in a bag grain bag in my bottling bucket.
3. cherry purees are the easiest, already sanitized and chopped, just dump them in, homebrew stores have them. Cherry extracts are even easier but some say they taste like cough medicine, you can buy them online.
4. 3-5 lbs for a lighter beer (wheat, blonde, etc) , 5-10 lbs for a darker beer (porter, stout, brown, etc).