My installation of JetPack was basically trashed; it no longer showed up among my installed plugins. When I try to install it, the install fails. I see:

Destination folder already exists. /home/content/76/8769676/html/wp-content/plugins/jetpack/

Plugin install failed.

If I manually delete the old directory (wp-content/plugins/jetpack) and its subdirectories, do I lose something significant that I haven't already lost? Or is there some way to re-install this without deleting anything?