As far as time spent, Jed claims the process takes around 2 years of serious work. I can only speculate but I wouldn't be surprised if that's correct. Destroying beliefs is a tough process but it can be done given someone puts in the time.
I also would imagine that Enlightenment through SA would leave you just as mindful. What is being mindful but seeing reality as it is? Julie, the girl from the 2nd book, points out that she "never vows to think again" as she sees it as a disgusting habit.
That being said I see no reason why it has to be "either or". Why not combine mindfulness with SA? This is what I'm currently doing.