Unbalanced is good.
I'm the same height and weight and boot size as you, and my board is a 159 NS Heritage. You'll be fine with yours. I'm going into my 4th season, and my experience is that the biggest stopper is timidity. Don't take that to mean you should throw yourself off the first cliff you see, though. Always limit yourself to what is logically the next technique or skill to learn, given where you are. But given that, being a wuss just slows you down.
Good waterproofing on the clothes, and I hope they're roomy -- too tight is bad.
Now where's my damned cookie?