multisites

My predecessor left me a huge online project and was sloppy with arranging images and documenting. Now I have to move the .com site and I am afraid other sites will break at certain parts. Are their tools to quickly discover where which images is connected to and to which domain and on which...

I want to install a new website on a subdomain. With DirectAdmin I'm able to install WordPress on the subdomain. This is the easiest for me, but is it as good as enabling multisites? Will my site get slower if I choose to install WordPress on it? Thanks a lot in advance :)