The most important part for SEO is the page title and the URL; you don't really want to change the url unless you absolutely have to.
The meta keywords don't factor into rankings so really aren't an issue. The meta description doesn't factor into rankings but is important to be written in a way that will convert the user by enticing them to want to click on your link instead of somebody elses.
If you want to just change the meta keywords and meta descriptions, you can clear them all and then re-populate those empty fields instead of deleting and repopulating which may cause various problems.
You can clear the meta keywords and descriptions with the following SQL Patch which can be run from the X-Cart Admin -> Tools -> Patch Upgrade section:
Code:
UPDATE wcm_cdseo SET cdseoKeyword='', cdseoDescription='' WHERE cdseoType='product';