In short, yes…;)
But it’s a process of integrating EE’s tagset with your existing HTML.
I’m writing a tutorial series on Train-ee where I’m doing just that: http://www.train-ee.com/courseware/free-tutorials/category/building-a-portfolio-site
On your second question - anywhere you want. You’ll just have to update the paths to where you stored them in your EE template code.
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