Hi,
If you update HikaShop, you should loose nothing. We keep all the informations.
The only things that can be lost are the customizations, if the developer used our override system by editing the views using the menu Display > Views you should loose nothing, else it's possible that you will have to add customizations again.
I think that you should make a backup of our whole website, and try to update.
Or duplicate the current website to have a development environment, and update on this environment to see if you loose anything and if the plugin is now working fine.