Since doing my 240 'under bonnet' one, I have tackled my 850's. That is under the car, rear end. The unions are 'simple push fit' . Well they were, surprisingly easy to 'undo'. However the cradle that holds the filter in place was 'dust' and literally fell apart as I tackled it! Of course that had to be replaced, prolonging a relatively easy job. But I know which one I'd prefer to do any day
