When your post is bigger than the box you should be able to scroll though it, or use the scroll bar on the right of the post. I don't know that there is any way to make the actual box larger.
As far as quoting, it's a matter of typing [ quote] and [ /quote] (without the extra space after the first bracket, on either side of the quote you want. You can either copy in sections, or quote the whole thing, and add the tags to quote the different sections. the key is for every start quote, there is an end quote (the one with the /. Practice a bit, and you'll figure it out!
