Drain the oil in the rear differential and check the color...does it have a lot of metal in it?Next get a magnet and fish around inside the diff..With the noise you discribe you should get lots of debris.It sounds like a diff gone bad.Buy a diff assembly from a junk yard and r/r it.Cheapest way...
Learn to start off smooth and have total control of your vehicle before you try.The main thing is for you to have total control of your car at all times when driving.If it takes you 90 years to master it,so be it.