Question on - Importing rule into grat tool

If i Import rules into GRat tool, will i lose the existing one’s.

Currernty, I have some 32 rules in Grat meaning 32 different work items.
we are planning to implement 50 more, so i thought of using the import option to import all 50 together using xml file, the same file can be used for Test and production environment.

thanks in advance