I
It's not hard, just need to be careful and clean, did mine recently and then did it again as the diff pinion bearing gave up.
Buy the Volvo filter and oil available on tbay,
EDIT
Read the fill up procedure several times it's a bit complex to describe but easy to do.
Take a look here:
https://www.freel2.com/forum/viewtopic.php?p=373780#373780