If you've put your customized template in custom folders (in the templates, languages, and languages/english directories per the FAQs you should be okay.
But be sure you make backups of everything, all your files and your databases, before upgrading.
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Just noticed that you're using 1.2.4. This may present problems. I think the entire philosophy of ZenCart has changed since the version you have was published. Other smarter and wiser folks than I will have to address that issue.



