The Questions of a Noob

So, I’m currently using a wordpress.com blog, but am looking to move it out and host my own version of it. But before I take that step I have some questions that I’m hoping people can help me with. I apologize if this has been endlessly answered, I looked and didn’t see anything that matched up…

Can I move all my old posts and everything to the new blog? Easily? How?

I was thinking about using dreamhost, any reason I shouldn’t or should use someone else?

I don’t have very much experience with any web design stuff, (i still have a geocities page that’s under construction from 1997…) am I going to be overwhelmed?

If I install wordpress on my computer, I can still post on the blog from any other computer right?

How do i do that?

I found a free, external theme that I want to use, is that going to be hard to set up?

What should I be doing before i make the final move from .com to .org?

What plugins do people suggest?

What don’t I know yet or am not asking yet that I’m going to need to know desperately?

Thanks!