I haven't done springs yet, but that sounds like the correct method. If you can get the spring out, the isolator should be an obvious swap.
I just bought some 2012 rear springs and am trying to decide if I want to replace the isolators or not (55k miles).
If you can jack the rear of the car up far enough to get the rear suspension in full droop you will not need a spring compressor. Take the lower bolt out that retains the shock absorber and the rear supension will drop far enough that the spring should literally FALL out.
As I look at the parts drawing, I'm not so sure that bolt needs to come out. It looks like it holds the suspension assembly to the floor pan, not the spring in place. Can someone verify? Is a spring compressor required instead?
Thanks!