Restoring a large course - alternatives

Hi everybody and thanks for any help in advance.

I have some large courses (more then 250 MB) and I need to put them in a new moodle site.

With my server I cannot modify php.ini, so I'm searching for some alternatives...

I have found this tutorial

But I have the last moodle ediction so...

How can I take my .mbz backup file, opening it changing the name with .zip, taking out some files and having again a .mbz file? 

And then, how can I put again the file I the files I took of? -Both using my site, both using cPanel.

And the last, opening my data site via cPanel where can I find the files of one course?? It seems a treasure hunt and I'm not good with it ;)

Thanks,

Elena