Did you have luck with FreeRTOS port using 547x/8x? Can you share?
The MMU will allow you to "partition" the memory of the part, you can also make 2 "partitions" look like the same address and switch between them on the fly. I have yet to figure out how to do this but working on it. What is your specfic questions about teh MMU? If you just need a basic setup for it, that is easy and the compiler startup code should ahve done it for you, if not let me know and I will give you a basic setup.
-Tim