regarding the marked phone after repair it depends on the form they have filled out.
If it has a section that states the quality of the handset when sent away then it should say there was no marks in which case they have to send it back with no marks at all. If there was nothin on their to say anything then it will be hard to get it replaced as there is no proof it didnt have a mark on it before it went away...
And guys WAIT for the v20 firmware on NSU... It will sort your probs out apart from the pic quality but then this phone is meant for videos not pics!!!