Changing URL

I have my WordPress site installed in a sub-directory called:

mysite.com/blog

I’m expanding the site beyond the blog to include services and would like all these new service pages to have the URL:

mysite.com/services/….

not

mysite.com/blog/services/….

which is what my currently installation will force me to do.

To avoid having to install a second version of WordPress at
mysite.com/

how can I do this? The most important thing is that all pages that currently have the URL

mysite.com/blog/[page name]

keep this URL as otherwise I believe it will mess up the Google rankings of these pages.

Thanks for your advice