I'm looking to change the trans and x-drive fluid on my 05 4.8is

I know the x-drive fluid is through the dealer, but how much do I need to get? also, what is the pn?

Also, is the trans fluid only available at the dealer? Should I do a simple fluid swap, or change the filter and do a complete fluid flush (car has 42k miles and has been lurching for over a year now).

Thanks in advance!

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