What you need is a "Flash Driver". That's a module that knows how to erase and write to the FLASH in your particular chip.
If U-Boot can write to the FLASH in that chip, then there should be a small number of files that you should be able to reuse to do the same thing.
Doesn't CodeWarrior or the Processor Expert come with this, or come with code samples that do this?
We wrote our own (for external Spansion FLASH on an MCF5329) but that doesn't mean you should have to.
Tom