Upgraded CoursePress to Pro – now MarketPress must be active?

I upgraded to CoursePress Pro. As you probably know MarketPress comes along and must be active for paid courses. I previously had this set up to go to a PayPal and all was good. My courses have been reset to Free until I activate MarketPress. I’d really like to know what is behind door and what I can expect out the other side. I don’t want a store here! I need very simple.