Migrating wordpress

So I setup wordpress in /wordpress off my site so that I could play with it and not mess up my current site. Once I am done I would like my root url to point to wordpress. I see that you can change the url. Does it copy itself into the root? How drastic is this and how safe is it? My other question is does anyone have any best practices for dealing with my pre-existing content. For example I have urls that other sites link to that I will want to now link to places in my wordpress site.

These other pages are easily simplified to
main,news,help
So if I want to have a help section for each category in wordpress, can that be acomplished with something like a sub category? For example I could have a category called “Some Program” and I would want a help category under that, and then a seperate help category under “Some Program B”. Any thoughts?

Finally whats the best way to handle my old urls, just put a blank page with a redirect to the new wordpress page?

Thanks!