PC world are renound for employing just about anyone. I have been in the past chased around the store being ask if I can be helped. I hate shopping in places that are on commission.
I would take the unit to their store and ask for written confirmation that the motherboard will last 6 months (preferably 12) from the install as they cocked it up. Also regarding the keyboard if it is due to their sloppy work I would demand they replace that too.
Off topic I just voted in the Poll and Im only the second voter. Who's the saddo (joke) who picked the second option? Every time I have ever voted before I have been about 400th in the list.