Hacker is gone but changes my dashboard

After 3 weeks I got the hacker out (I hope)of my wordpress blog but has left damage. Most of my dashboard is gone, no author names, no plugins or path to install, No appearance, no widget. In the article area I have no option to edit or trash the bad blogs left behind.
Is it possible to reinstall 3.6.1 somehow without loosing the articles I put on this website and will that reinstall all the left side words?
Or is something else have to be done to restore the website back to what it was before the hacker came around. I am afraid if I take the backup from my external hard drive to do this I will reinstall the hacker back into my system and I do not need that!