I can't be sure about your questions 1, 2, and 3, but question 4:
It's free, and really quite easy to do.
As for the other questions, you might look at Teli Adlam's "OptiNiche" for ideas.
She has a "Digital Product Manager" which is a plugin and accompanying guide, but it may or may not be outdated. I haven't tried it. It dates back to 2007, so I'm not sure.