I have an older Brother that had a broken gear. Getting that gear off the main drive shaft is really, really hard. I have a family full of mechanical engineer-types who tried, and the conclusion was that you have to have a specialized tool to remove the shaft and get the gear off. I wonder if those repairmen you talked to even have the tool. I agree with other posters who say it would be less expensive and better if you purchased a beginner's machine (with adjustable speed) for your niece.