I read your other posts. I'm afraid the reception here is not going to be any better and could easily be worse.
You're flying head long against everything that has been written all over this place, including this stickied thread available at top:
http://forums.studentdoctor.net/showthread.php?t=346106
I don't think you're headed toward a cliff. I think you're shooting past one! That many courses from Harvard Extension from the start is likely worse than the early part of any SMP. I'm horrified that you're going to take a sledgehammer to the jewels and never walk again (pardon for the language).
... but I feel like nothing's going to dissuade you now. Looks like you're signed up and probably signed contract and everything.
All I can say is good luck. I say that seriously and honestly. I wish you the very best and hope very, very much so that you prove me wrong.
I don't know when classes start, but it's not too early for you to prepare. PMing previous students for their notes and/or practice tests. Brown nose, beg, cry, bribe if you have to. Find the A students and ask precise questions and do more than they did. Because of your past performance, you have NO option but to compensate.
If they studied 2 hours for so and so, you will study 3.
If they did 50 practice questions before exam, you will do 60.
If they reviewed notes 2x, you will do 3x.
If they did X, you will do X+1. Be it on your head if you do not do this.