How do i remove the driveshaft from a pug 106 1.5 deisel??? ?

I have sourced a replacement driveshaft for my girlfriend's 106 1.5xnd. I am having a bit of trouble in how to get the old one out. I have removed the Brake caliper and disk, and tried to undo the link from the end of the steering rod, but the nut on this just turns the stud around, without undo-ing. Need a bit of guidance on replacing the driveshaft if possible, as i have a fair bit of knowledge working within engineering (ie it will, be done properly) but im not a mechanic unfortunately so dont know the take down order.
I have looked all over the gearbox also, to drain the oil before taking the driveshaft out and change it once finished, but cannot find where to top it up either, as not too sure of what to look for???