Hey Trevor!
No it doesn't have to be fully installed, but i can say from experience getting parts for this model is complete !&&*. I stopped working on them because of this.
I'd first make sure the LCD is compatible. Is the flex on the new LCD the exact same as the old one? If not, it wont work. And if it is in fact the wrong screen, chances are the touch screen won't work either since since it's plugged into an incompatible LCD