Toyota Repair: abnormal noise from differential

Question
I have a 2003 AWD Matrix that was towed improperly. It developed a whining noise that gets higher in pitch with speed. After researching I found a Toyota Service Bulletin DL 002-07 ABNORMAL NOISE FROM REAR DIFFERENTIAL. It identifies the problem, parts and repair procedure, but I have no idea of the cost. I need a ball park figure to see if I want to invest the money into a car this old. Someone suggested I convert to front wheel drive. Is that possible?

Thanks

Answer
Looking at the service bulletin the time allowed by the factory is 7.1 hours to complete this operation, the dealers almost never use "warranty time" for customer pay work, so it will be more like 12 hours customer pay, you can try to negotiate that depending on the circumstances and willingness of the dealer management, the 12 hours translates into about $1200.oo labor since most dealers are at $100 or more per hour labor time, I'm not familiar with the parts prices and I don't like to guess so add the parts prices to that, the part numbers are listed so a quick call to the dealer would give you that information, my best guess would be around $300-400 for the parts.