Convert a Template to a Website

my website is currently using zen cart ver 1.51 and i would like to change template for it that purchased from elsewhere, but the template provider request me to delete old content but i would like to keep all customer details and order details. so here is the task: 1. reinstall the zen cart and keep all customer details and order deatils (template installed is no need i have another team work for me) 2. once this task complete i will have another a few tasks need to be done afterward