Toyota Repair: 1999 Sienna Differential noise, differential fluid, salvage yards

Question
I have 1999 Toyota Sienna which is making noise, I though it might be drive axle on passenger side and changed it. but noise still there.
I lifted car on jack stands and tried to here the noise, I am very sure it is coming from differential.

Noise is like grinding something/like dry bearing etc. Sienna runs fine no shifting problems at all, no slipping, no engine light, just the loud noise.

turning does not make any difference in noise. I took to transmission guy which said it will cost close to $1000.00 to fix it.

I was wondering if I could get help on how to change differential fluid which I never did before and see if it helps.
Or if I can get advice on changing differential bearing if I need to do that and how hard is it?

Thanks

Answer
If it's already making noise then changing the fluid won't help, don't waste your time and money. Most repair shops do not repair differntials because of the special tools involved and the expense of the parts. Most salvage yards that specialize in japanese cars whould have a complete differntial at a reasonable cost so I would try to locate a used one and have it installed, you will probaly save about $400 this way.