The upgrade itself isn't really needed in this cause cause I can see -why- you're using 1,900mb. There's a 1.9gb error_log file on your account, which is why the site's using so much disk without a reason.
I went in and trimmed all but the last 10 lines of the error_log in case you hadn't seen there was an infinite loop on 9/25; the current disk dropped to around 6mb with that as well, but your cpanel should allow for uploading again.