Swapping trunks is easier. Done it 2 times on my bonneville. Not sure if a 2 door and a 4 door trunk are the same depth, but if they are, then it'll be easy and is best done with atleast 2 people, 3 works best. Open the trunk all the way up and look at the sides. The bonneville trunk had 2 bolts on each side that held the trunk on the hinges. You remove those bolts and the wiring harness and the trunk comes right off. Here is some of the trickier parts. If the trunk wiring doesn't disconnect at the hinge, or near there, you'll have to pull it through from the lock area of the trunk. Remember where this slid through as you'll have to fish it back the same way in the new trunk lid.
With the lock, on the bonneville you could reach in and there was a retaining clip that you could pull out. When you pulled this out, the lock could then be pushed through the opening from behind, so that it popped out to the front. You would then replace it the same way, making sure to alight the bar that turns when you replace it.
The reason I said 2-3 people is so one of you can be on each side and if there is a third, they can do the wrenching. This will same you from messing up the trunklid and from messing up the back window. On mine, I can swap the trunk with 2 other people in less than 30 minutes. i removed one by myself in an hour, but messed up the trunk edge a little and didn't have to worry about the window (cause it was in a junkyard and I broke it.)
2007 Saturn Aura XR | 1970 Chevy Blazer 4x4 | 1970 GMC 3/4 Suburban 4x4