Upgrade Flow for 10.2.400.9 going to 10.2.700

We are planning to upgrade from 10.2.400.9 to 10.2.700. Would like to know what should the order of upgrade be, given we have to update our QuickShip Pro and also have CRE. A lot of questions come to mind e.g. should QSPro be upgraded first and then Epicor? Could we update Epicor for PILOT account only and have CRE and QS updated to work with the .700 and it wouldn’t break running the older version on LIVE?
So any help in what should the installation flow be OR steps that someone has gone through going upto 10.2.700 would be great!
Tips, advice all welcome!