How to "RESET" a WP site at the level of Host Gator

I have a site that was corrupted, and I would like to completely "reset" the site by doing a totally fresh installation in Host Gator.
If possible, I would like to leave my media files intact.

I am going to install a completely new theme, plug ins, etc.

Can you help me by telling me what to DELETE at the level of the domain...and what to leave intact?

Also, I have SUB DOMAINS under the main domain, which I would like to leave intact.

Please Help me out...or point me to the right spot where this may have already been answered.