The first tip I give to people is backup, backup, backup. 
The second tip: gig files are ‘project files’ – you save one project, close it and open another one. It will not affect your any other projects.
You can have two projects at once! Create a new Gig Performer instance, run it, load the desired gig file and you are good to go.
Helpful link: [blog] How to use multiple instances in Gig Performer