I'm assuming you're asking about the fluid changes.
Yes they can both easily have their fluid changed without a lift. Will will definitely need a good jack (I have one for "SUV"s so it has a high lift of I think 22") and 2 jack stands.
I usually put the passenger side up to change the bevel gear fluid because the studs (and thus the make-shift drain) face that way.
I usually put the driver's side up to change the rear diff fluid because the fill plug is on that side.
I have read conflicting reports about the limited slip additive requirement. I think I read in the 1998 V90 user's manual that the limited slip additive is required. I think I read in the RWD FAQ on this site that the Eaton locker used in these diffs does NOT require the limited slip additive. I put it in for good measure, as I'm pretty sure that it won't affect anything adversely if it isn't needed, but it would be a problem if it was needed and I didn't use it.
I am not sure if there would be any real damage from not using the limited slip additive or not - it will help eliminate "locking shudder" but I don't know if "locking shudder" is detrimental or just annoying.
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1998 V70 AWD->FWD Turbo 200k+
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