Will this SSL Certificate Solution Work?

I'm having some complaints of people unable to access my site from work or other computers. I've been told that I need an SSL Certificate.

I'm running an MU community with 300+ members and growing.

First, is it true that I need one?

Second, I've heard that SSL Certificates and MU are tricky...Godaddy has a "single domain with unlimited sub-domains" package for $199.

Will this work with MU?