Hi Tofskilemons,
The window on the stairwell has to be cut out to make the extra section .
Mark out the area on the model to be removed , with a black felt tip pen.
Now you have to remove the section , so i drilled several small 1/16 holes around the area's inner edge . You can eventually move the drillbit in a rocking motion so as to join the holes up.
You should then be able to remove the majority of section out.
Then carefully spend time filing the area to the finished size till happy !
As for the windows , just cut two strips of 40thou glazing to fit the lower deck sections, and make a tight fit in openngs.
When trapped in place , mark where the vertical glazing bars are by lining up from the upper deck ones. They also line up with the lower deck body moulding joints.
These should now be masked and sprayed with a satin black. When thoroughly dry , remask to do the horizontal bars (top and bottom plus vents )
When the model is ready , glue the glazing in with 2 pack adhesive almost flush with the outside.
Another problem you will encounter when you have removed this window , is that the back of the staircase is visible, so that has to be reduced in length so as not to obstruct the new window !
Just a word of warning , the rear is totally different to the Mk 1 model casting , and i had to rebuild the whole rearend and slightly alter the side shrouds also .
Let me know if you need advice on this area also !
Hope this helps !