I'm not sure what an "open box" copy of WPX8 means ... but if it is an OEM version then you could be in for an adventure. ;-)
See (for example) "Should you buy an OEM (Original Equipment Manaufacturer) version of WordPerfect from an Internet source?" here:
As for Corel "breaking something that doesn't need fixing" -- please be aware of a few things:
 Windows itself has changed considerably since WordPerfect X4 was released in 2008. (Windows Vista was the current OS back then.) Hence software products that run on modern Windows versions might need "fixing," especially since Windows is now at version 10 (released in July, 2015). While some users have not seen problems running WPX4 on Windows 7-10 (as reported on various WP sites), others have and so they have upgraded WP as a solution.
 Corel, like many software publishers, supports only the most recent versions of its products. With WordPerfect they currently show downloadable patches for WPX7 and WPX6. (WPX5 patches, released in 2009-2012, are still on the Corel.com Support page, but IMHO perhaps not for much longer.)
 As said, while earler versions might work reasonably well for many people on modern versions of Windows, the only guarantee you have of that is found in the System Requirements listed on the Corel site for each version. Note that WPX8 has been out for nearly a year and no patches have yet been released for it. Note also that new releases of any software program often contain fixes (rather than separate patches) as well as new features. I have found that WPX8 is extremely stable on Windows 10....