so if i change the logic board could that work? and is the storage soldered as well?
It won't work/fit. Basically no parts are transferrable between generations. I don't want to say "no" parts are because I am sure there is something... but 99% of the parts will not transfer. Probably screws are the only thing I can think of from the top of my head. They change layout slightly, screw hold points, battery size, logic board shape, etc...
These are very compact devices and every square millimeter is accounted for during design to make them so slim and compact. Even something as small as the "Home" button will not work between generations.
My suggestion would be to sell 1 broken model to get the money to buy the screen for the other.