To check if it is the desired multiblock make if checks like (pseudocode incoming)
if(world.getBlock(x,y,z) == Blocks.stone && world.getBlock(x,y,z)==Blocks.wood) setBooleanToTrue()
I dont know what the getBlock method in 1.7 was so u need to find that out urself.
And about the texture. I think you could use metadata to do that