I've only ever had to repair an odd broken key or 2. The sort of job where you could do with an apprentice. Show him how to fix one key and let him get on with the rest. What we were given 5 fingers on each hand for. One finger to hold the spring against the frame, so it doesn't fly off, one finger to hold the key back against the pivot and another finger to push the other loop of the spring over the spigot, while pulling the spring with a dental hook in the other hand , and then a satisfying clunk.