Yes you can install your own GPS. I even think if you have it already you can send it to PCS and they will install it for you. I would contact them about that to get a fir, verdict though!
You should be fine installing the card yourself,just be careful and make sure you take anti-static precautions before proceeding,even if it's just touching a bare metal part of the case/PSU.
You can still install it on your own. I believe that even if they install the GPU and it causes a problem it will not be covered by the warrenty, again double check though.
Rack is correct - however it is a very easy process installing a graphics card, as Vanthus has said if you take anti-static precautions you should be fine
I've changed loads n loads of parts within my pc, so you will be fine, But alot of other companies dont like you doing so, but pcs are more than happy with it, like the others say just dont break anything lol
Well yea i was asking in here because i didnt really know where to look for the answer on whether it would affect the warranty lol :/ like i mean if their psu screwed up etc and it led to the damage of the motherboard+gpu would they just replace the motherboard as i got that from them or would it include the gpu too, the live chat pcs supply i found was pretty rubbish because the woman who was speaking to me gave me an answer completely unrelated to the question! D:
+1 to what Vanthus has said, it is unlikely they would replace your gnu for you if they did not supply it. You would need to RMA it yourself with the manufacturer if anything happened. if you give PCS a call you should be able to get a definitive answer pretty easily.