If you don't have a spring compressor the easiest way to remove it is to fit the shock on to the bike and get somebody to sit on it while you twist some wire around the top and bottom coils of the spring so that when the weight's taken off it can't stretch.
Then it's easy to slip out the collets and remove the spring. Leave the wire around the spring to keep it compressed until it's refitted.
No resetting involved ecxept you'll obviously have to re-set the preload adjustment. Best to have the shoch refitted and weight on the bike before trying to remove or cut the wire.
I was in the same place about a month ago. Seems like the easiest way is to get spring compressors. Unfortunately no one in my town sells them and I am impatient. What I did was take 2 aluminum plates. I drilled a 2 1/2" hole in one to fit behind the spring adjuster. I drilled a 3" hole in the other plate to fit over the other end of the shock. I joined the two plates with threaded rod. I tightened down nuts on the threaded rods to compress the spring. Worked flawlessly.