you can rent a spring compressor from Performance Products, its $85 for 3 weeks.
As for those spring pads, they're made of rubber and are in a pretty safe spot so deteriation isn't a problem for them.
Your sag seems to be from a single person driving the car all the time without any balancing loads, that side of the car's springs are tired. You could try changing out all the shocks (don't do just one side, just causes problems). You can do that without the spring compressor even.