you don't need to disturb the large driveshaft nut. you will, however need a 7mm allen key. remove 2x 7mm allen key pins to remove caliper. remove caliper carrier (2x 18mm head bolts if i remember correct).
remove disc. they quite often rust onto the hub so may take a bit of persuasion.
reassemble is a reverse of removal.
as with all things, if in doub't don't and leave to a garage. remember its your daughters car etc etc.