Sorry for the noob questions, but the manual just isn't clear and I'm getting different answers from different shops.

On page 9 of my manual under "additional maintenance" it says "Controlled four-wheel drive 911 turbo: change oil". What oil is it referring to? One shop says that the rear differential shares fluid with manual transmission and you change that and you also change the front differential oil. The manual also mentions "four-wheel final drive: change oil" every 12 years. Is this yet another fluid or is it one of the other fluids? I feel so dumb, lol.