Quantity of workout

How much workout should I do a week? How many times a week?

Depends on what results your looking for. Generally three times a week for an hour is good. If you dont curently work out start by shorter and less intense workouts then gradually increase it.

A workout is base typically on what you wish to achieve. For an example I'll show you mine:
Summer
mon-off
tues-chest and bi's for 2 hours and 30 min cardio
wed-shoulders and back for 1 and a half with 30 min cardio
thurs-benching for 1 hour, cardio for 45 min
fri, sat, sun off

all other seasons
mon-2 hr workout
tues- 2 hr workout
wed- off
thurs 2 hour workout
fri- 1 hr workout
sat and sun off

Now I work for strength and endurance training which means I do 5 sets with max reps is why it takes so long for. But you have determine the characteristics of your own workout based on your goals. try checking out http://www.muscleandstrength.com/
that should give you some good routine ideas.

I would say 3 times a week with at least an hour workout and maybe some extra cardio.