When you uninstall, MC gives you two different "things" you can remove at the same time:
1. Settings
2. Your Library
Settings contains all of the options under Tools > Options, the settings for the DSP, and any Zones you may have configured. This would include things like Auto-Import settings, custom Video and Audio setups, etc.
The Library is the master database for MC. It includes essentially everything else: All files that are imported and all their metadata, all of the Views in MC (those in Standard View, Theater View, and Network/DLNA modes), and all Playlists and Smartlists.
Both are contained in the automatic and manual Library Backups that MC makes periodically.
Removing both of these would reset MC back to a completely blank slate state if/when you reinstall. Removing the Library is especially "destructive". This would cause you to lose any Library structure customizations you made, and all metadata not stored in the file tags. MC does store most metadata in the in-file tags where it can, but not everything (especially play and library stats like [Number of Plays] and [Date Imported]), and not all file types have robust in-file tagging support (especially video files, if you don't have the sidecars turned on).
Completely uninstalling and removing both items would probably be a pretty drastic action, and may not solve your problems (which were undescribed). Without knowing more, it is difficult to make a recommendation, but that does seem a bit akin to swatting a mosquito with a sledgehammer. I'd certainly recommend that this only be done as a last resort, unless your Library modifications have been minor and all metadata that you care about will be preserved or easy to recreate (based on file structure or something).
