The questions would be:
What does the other side of the car look like? is it OK, or nearly as bad?

Do you want the entire panel replaced, or just the bad sections? Replacing the entire panel is likely going to revel more rust, at what point do you want to stop?

Its very likely, the rust damage involves everything that is attached to the part, in the area of the rust holes. The damage probably extends at least 3/4" to 1" on either side of the rust through. A patch can be welded in to replace just the damaged sheet metal that may last many, many years. The downfall to that is if some rust was missed, down the road 10-20 years, it may need to be addressed again. A patch would be fine for a driver, or occasional show car, but probably not OK if your going for the 100 point show car.

Like stated earlier, there are no replacement panels for this piece, its going to have to be hand formed. Replacing the entire part is going to involve the trunk floor, the trunk floor extensions, the tail light panel, the frame rails, the leaf spring reinforcement plates, and the rear end of both of the rear quarters.

Other then that, its easy, anyone can do it.....