Large Scale replacing

I build a massive building, but I don't really like the roof, I want to replace the slabs/stairs that I used to a different type, without compromising the exact locations how the slabs are placed, or the direction the stairs are facing.

When I replace, they all face the same direction, but not the original direction, and for slabs, if they were the upper part of a block (or lower in some cases) they are misplaced to the lower parts.

Is there a way to use other commands? I tried finding it in documents but didn't really find anything, brush helps slightly but it's only block for block, and I still have to do a decent amount of self modifying.

Any help would be greatly appreciated.

(Maybe important info, It's a japanese style house/building) meaning roofs go up & down, with corners going slightly up. Also, the smallest building has (in total) 142,500 blocks