Hi,
2.
Here
is more information about what to do when you get a blank screen.
1. By updating HikaShop you won't loose any information. It will just upgrade the files and add new columns in the database if required.
Your views overrides, css [/b]overrides[/b], language, configuration, orders, products will stay intact.
But careful if you have modified directly an HikaShop file and you didn't use the backend interface for that. Because you could loose your modifications.
Making a backup is always a good security.