The spring almost certainly has a fair amount of preload(unless it broken of course). While it is possible to disassemble some spring guns without a compressor, I wouldn't try it. Even uncocked the spring can do a fair amount of damage if it gets loose. If you do manage to get it apart, putting it back together can be a problem also.
Maccari spring or not, it'll still bend or break if the guides aren't long enough or don't fit the spring right.
In your initial post you said that the action had smoothed out- did you mean that any vibration or noise had gone away? If thats the case, its because the spring was slowly bending. A spring with a slight bend will still work, but parts of the spring will be tight against the guide, and there will be no spring vibration. However, whatever is causing the spring to bend will keep bending the spring a little at a time until it reaches the point where it either starts hitting something or breaks.
If the gun is fairly new, I'd call the dealer and see if its warranteed.