Hi,
The product "upgrade from essential" will change your current "hikashop essential" license to a "hikashop business" license.
If you buy a HikaShop business license, you would have two licenses. One for the essential and one for the business.
So I recommend you to buy the upgrade, the price of this upgrade is the difference between the essential and the business versions.
It was like you bought hikashop business and you would have the same package.
After that, upgrading HikaShop is like update HikaShop. You wouldn't loose your configuration/products/overrides/etc.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.