You should not lose any products as they will be stored in your database and the images that go with them will not be over-written (unless you have used the same file names as for Zen Cart's demo products, which is very unlikely). If you are currently running a version of Zen Cart prior to 1.3.7 then you will need to upgrade your database by running the zc_install script in your browser. As long as you "upgrade" and don't "install" your products will remain safe - though don't forget the first, second and third rules of upgrading: backup, backup and backup.
If you have constructed them properly as over-ride files then they will be safe. If you have simply edited your changes into the files that come with Zen Cart, they will probably be lost, so this would be a good time to read the FAQ and Wiki to learn about over-rides and ensure that you have a backup.




