Device up-gradation consideration
these are thinks better to consider while upgrading the device with the newer one .
power [ AC/ DC / socket type ( C14/C15 - C19/C20 etc)
Rack type and mounting brackets and screws
IOS Feature comparison does all the features supported in the newer image - double check [ sometime we downgrade the device eg: move the powerful device where most needed]
Access to the technicians
Interface Type and fibre patch cords [ lc / sc / fc ] , length.
If we are swapping the device from different location make sure the transport and proper wrapping / cartons.
Then actual migration plan :)