Hi Susan,
There are several ways you could go about this. If you decide to install WordPress in the root folder and leave the /blog folder intact, you'll probably end up with two separate instances of WordPress with separate logins, etc. The best solution would most likely be to move the entire WordPress installation and then assign a WordPress page for your website's front page and also for the blog section (with a slug of /blog). That way, the blog section would appear that it had never moved at all and the new WordPress-powered homepage, secondary pages, etc. will all start in the site root.
Here are a couple articles describing how you can do this: