Installing a new upgrade should not damage your existing files in any way.
Having said that, it is ALWAYS a good idea to make a backup of important work - such as 200 custom imported discs - before doing an upgrade.
Every Hoster user should have a backup hard drive that you religiously backup to every time you import any new songs. It is easier to restore that reimport, and hard drives are cheaper than your time to import, even at $1.00/hour labor costs.
MTU offers several backup hard drive options. Contact MTU Sales if you need help in choosing what is best for your needs.