How to install Multisite to run 2 websites with existing frontend static content

I am new here, also fairly new to WordPress, and have a couple of install questions:

I want to install Multisite 3.3.1 as an add-on blog and then run a second url from this install. Both sites already have existing front ends. I see the Multisite should be installed at the root. How should I install it to not overwrite the homepage at the front end?

For this install can I use the Multi-Domains plugin and then point blog 2 to something like “site2.com/blog/” for the second site?

Thanks