The situation described would suggest that loading Rockbox onto it is an impossibility.
In order to install Rockbox on this, you need to OF (original firmware) to be able to boot, so as to get access to the internal storage volume. Without being able to do so...well, you get the idea, I'm sure.
Secondarily, why even take the risk, when there are so many working second hand and refurbished devices available?
[Saint]