Not knowing your engine, I got curious about what was involved for oil pan removal compared to the 4-cyl engines so did a quick search. I came up with this old thread in the Volvo Forums to help get you started.
https://www.thevolvoforums.com/threads/deep-trouble-1997-volvo-960-oil-pan-removal-has-anyone-done-this.7860/

Seems removing the cross member isn't enough and engine removal is the way to go.

Are you mostly wanting the pan off for an inspection or just a good cleaning? Thinking out loud here, I'm wondering if you drained the oil down to the last drop overnight, letting it settle in the drain pan, then slowly poured off the top, that you'd see in the residue what kind of grunge you're up against before trying to start it for a flush. Be sure to run on synthetic, not dino oil, if you want to do a better job of getting deposits out then do an early next oil change. I'm also wondering if you can lay your hands on an inspection camera with a narrow scope you might be able to get it up into the drain hole for a partial inspection. I see a cheapo scope on Temu for around $50 that's 7mm diameter (a hair over 1/4") and listed for auto inspection. You could even look down into the spark plug holes. A lot less work than engine removal if you're not yet certain the pan needs to be off.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now