The springs you can retain, its just the shock absorbers you need to replace if you want to reduce the stiffness of the ride. I fitted standard springs to the comfort ride shock absorbers and I have to admit, I think the feel of the suspension is bang on. I think my shock absorbers were My05 spec or possibly LE500 ones, which could be the same unit.
I fitted standard springs, but opted for new powder coated ones, but if there is nothing wrong with your old ones they will be ok.
Sundance