That "might" be necessary for fan removal, but unlikely for the sensor alone...it should be accessible from under the car (easy to get to on D2 model).
BUT once again, I don't have the Bentley manual for your D3. Take my advice and order one..you'll be smarter and happier..it will pay for itself with the first unnecessary repair avoided.

And remember, when fan control units fail, they almost ALWAYS stop turning the fan...not shift to top speed...and 2 of them doing the unlikely at once? ...there's no number high enough to calculate THOSE odds

Good Luck & Merry Christmas

 

does the vehicle not have both a temp sensor and a temp SENDER ?

 

Same problem. Help!!!