Yes,
What it amounts to if you want the least amount of downtime is you need a way to configure your 5/05 ahead of time, so it needs to be sitting in a rack that is identical to the one you will be running.
You can get an exact copy of the rack you are using now, all same I/O. (But no 5/02 processor)
Then insert your 5/05 processor in this rack, set up the new processor for given I/O configuration.
Upload the program from the working 5/02 and change the configuration to match your 5/05 processor and controller communications as necessary.
Then download the newly configured program into your 5/05 that is sitting in your new mirrored rack.
Turn off power on the mirror rack, remove the 5/05.
Turn off power on the original rack, remove the 5/02 and insert the 5/05.
Turn power back on to the original rack.
Then you should be off to the races....barring any odd comms configurations such as Mr. Beaufort pointed out.
Or if you can stop your process for just a little longer, forget about the mirror rack and bring your process to a stop, turn off power to the rack, swap the processor, configure the new processor and your program to match, download the program to the new processor sitting in the old rack and then restore power.
I just did this going from a 5/04 to a 5/05 and it did not take very long at all.
You just need to make sure you have your ducks in a row when it comes to how did the old processor communicate (DH485...RS232....etc) compared to how will your new processor communicate (Ethernet...RS232...etc).
What kind of process are you running that cant be shut down.
BCS