I would suggest to go to a specialised place. Many garage has stopped to do it due to the risk associated with it. One garage owner that I know actually stopped to do it when the spring slipped out of the compression tool, flew about 50ft in the air before touching the ground, bounced off about another 20 ft.... and it ended up on the other side of the street... about 200ft from where it was initially.... That was their last one they did, they are lucky that the mechanics that was moving the coil was unhurt (could have been seriously injuried or decapited!) and that there was no car in the parking lot (they also serve gas) and that somehow the busy street had a quick time where there was no car...
Now what they do is: have the coil removed by a specialised place, have the car tow back to the garage, they do the repair, the specialised place tie the coil with a few turns of metal strapping and send it back to them, then they install the compressed coil then cut the strapping. When the straps break the car almost jump off the ground. That should give you an idea of the strength of the spring.
I personally can do lots of things on car, I did many dangerous stuff too. I'm affraid of working with coils, I saw the tools (think of a V with a screw in between, and a clip on the end, you just put the 2 clips on the spring and turn the screw, which bring the V closer... if the spring go ( it can get out, or if the clips slip....)
Specialised shops have a machine that grab the spring on both side, they compress, strap it, then remove it....
when I had to do the job on my cavalier 1993... I did researches, but I opted for safety. it took the garage only 1 hour for both side, very well invested money. That is the only repair that any garage has done on my cars.