Escaping and replacing a corrupt theme

WordPress 4.3.1 running Twenty Fifteen theme, on a Linux platform.

Seems as if my original theme, [Go Daddy Techtra Version: 1.2 – By CyberChimps] “gdtech” file directory got corrupted, perhaps with the installation of the plugin “external-db-auth-reloaded”. I renamed “gdtech” to “XgdtechX” and that apparently activated the default ‘Twenty Fifteen” theme to be the current theme, which enabled me to re-enter <mysite.org/wp-admin/.

Now, can I delete the renamed “gdtech” directory – “XgdtechX” and reinstall/activate a new ‘Go Daddy Techtra’ theme (the same as the original) without losing all the customization of the pages ? Or is there another solution to this problem. I’d be glad to know!

Thanks!