On my Landmark, I have a 4 step manual pull out from factory. The current electric steps (like Kwikee) are max 3 steps. They do not cover the full vertical distance, the last step would be a "big step" (pun intended). The retrofit mounting would be different as well.
Not to sound too negative, but it would not be a simple modification.
There was a previous discussion on this and I'll see if I can find it.
Take care,
Brian