You can generally tell the type of disposition the hedgehog has by holding it and observing it's reactions. An energetic, lively, explorative hedgehog makes for a good pet. If the hedgie is diplaying these behaviors, it is often a good sign. This isn't too terribly tricky. The female genetalia is located at the base of the tail.
Housing is really up to the individual.
20 gallon fish tanks is what I consider to be the minimum amount of space required. Large auqariums, large plastic storage bins, rabbit cages, or home-made cages all work well. Its just important to consider the hedgehog's needs when buying or making a cage. Because exessive body fat can be fatal to hedgehogs, a low fat, high protein diet is always a good idea. There are special hedgehog diets on the market today, one being Brisky's, which Misty Valley Hedgehogs is a provider of.