You could view the source code and then save it as a text file, and then edit it using your text program, save it as "index.txt" (or any file name as long as it's saved as plain text), and then upload it and install it with the name of the file you're updating.
Knowing some basic HTML would help a lot. That's why I always encourage people to learn some HTML and not be too reliant on a particular Web editor.
You can open the site in frontpage by using the open web commmand on the file menu and the typing the full url of the website into the box eg "http://foo.com"
You should then be prompted for the username and password for the website. Enter these details and the site and all files should be visible on your pc. You can edit your site and also change passwords, create subwebs and change permissions(live) this way before saving it to your pc. Simply choose publish and then type a local path on your PC to publish to.
By default when you next open frontpage it will open the last web you worked on which will be your live website so, make sure you close this and open up your local copy now (hopefully) on your hard drive.
"Publishing" back to your harddrive usualy keeps all the navigation structure intact as well which has always been lost when I have tried "importing" a website.