new sunroof?

i prolly wont actually do it but its just a thought. . . . weather i do it my self or have a shop do it, would it be difficult to add a sunroof to a car that doesnt already have one? i have a 92 SC2 and the liner is torn out the inside roof is a lil messed up. im considering on adding a sunroof while im fixin the liner and all. kinda kill two birds with one stone kinda thing. if it is possibly does it have to be a saturn brand sun roof? can it be from any other brand or after market? are there and rules id have to follow when lookin for one? like if i want a power sunroof with one of those shade things on the inside, could i do that? well thanx in advance.