I was going to upgrade Magento 1.7 site to Magento 2.0.
But Magento 2.0 has different structure.
Is there a way or tool to do this?
Lastest Magento 2.x version(2.0.1) ,Add tool Code Migration Toolkit by which you can transfer your 3rd party extension of 1.x version to 2.x structure.
Magento 1.x module structureto
Magento 2.0structure using Magento client Cli tool
See the full steps of migration at Code Migration page
you should have strong knowledge of Magento 2.X structure Thus you can convert 1.x code to 2.x.You can understand those thing from code-migration process
But honesty ,you need to do lot of works for this achieve .
Magento 2 is not backwards compatible. There exist migration tools, but the general advice has been to treat a 1.x – 2.x upgrade as a re-platform.