Nimbostratus
CirrusI found this article to be very helpful when I started looking into this Converting a cisco ace configuration file to f5 big-ip-format And this is where you can find the perl conversion scripts Cisco Ace to F5 Conversion Scripts
Now from a personal experience doing an object by object conversion is the best way to go but don't forget to take in account some of the nice feature F5 provides. You might have to completely change your design when moving to F5. Take in consideration all the factors of your environment and how you get utilize the F5 to it's full potential.
Hope that helps