Upgrade from SAP PI 7.0 to PI 7.3

Hi Experts,

We are planning to upgrade our PI system frm 7.0 to 7.3. I saw so many documents in SDN but I am confused frm where to start.

Can anyone please provide the details like what are the things I need to consider before moving to PI 7.3 and what are the steps need to to install.

Thanks

Raju