I had to replace an upper strut mount, turns out it was pretty simple. The springs are light and can be compressed using a spring compressor and a 3/8" drive ratchet -- by hand. Be careful that the spring compressor doesn't slip, as that would be bad.
Actually, I would be surprised if you couldn't just jack the car up high enough on that side for the spring/strut assembly to unload. The spring's free length isn't too much greater than the extended length of the shock.
EDIT: When you go to rent the tool to compress the spring, you need a strut compressor.