If you're switching from a github alpha (debug) version, this version will install side-by-side with your current version, so there should be no risk of data loss. However, it's always good to backup your settings, layout, icons, and wallpaper anyway, and this will also let you restore these things in the Play Store version.
To create a backup of you current Lawnchair settings:
- Open the "Home settings" by long-pressing anywhere in the blank space between icons on your home screen and choosing "Home settings".
- Use the three-dot menu in the upper right to choose Create Backup. Save the file somewhere handy.
- Later, restore that backup in the new version of Lawnchair.
It's weird having both versions installed. When I open my app drawer and search for Lawnchair, I only get one result, and now that I've restored my backup, I can't even tell which version is being launched when I tap that icon. Thankfully the alpha version is named "Lawnchair (Debug)" in the Apps list, and I can now uninstall the debug version.