My Door Wont Close

So my drivers door wont close and stay shut. I have come to the conclusion that the mech. inside the door is busted. So I am going to swap it out. I am wondering if this is a straight foward swap or not? What will I be getting myself into when I rip this door apart. And I have a 92 and I have some parts from an older 89, will 89 door mech work in my 92??

Thanks
Chris