cpu pins damaged ?? no idea exactly what you mean by this. have you removed it and physically damaged something in the motherboard socket?
you shouldn't need you to take everything apart either.
don't know if any damage was done to the cpu or motherboard by you connecting the wrong lead,
fingers crossed it just meant the cpu wasn't getting the correct power it needed to run so simply connecting the correct power lead to the cpu power socket and then the now 24pin connection (20+4) to the motherboard 24pin header and turning it on will power up the pc.
if it still doesn't power on then yes it isn't looking good and damage may have been done to either the motherboard or cpu and you'll have to go through the return part, rebuild process.
when contacting seller about replacement, don't tell them you connected anything wrong, just say when everything was connected correctly it wouldn't power on so think the part is bad and want a replacement.
before starting any returns tho first make sure all the correct power leads are connected and see what if any lights appear on the motherboard when attempting to power it on, also if the case or motherboard came with a speaker connect it and see if it makes any beebs, these are error codes and should be listed in the motherboard manual.
don't know if you did or did not fully read the motherboard manual but if not i suggest you do again, just to triple check everything especially troubleshooting any codes the motherboard may be giving to let you know where the problem is.
Edited by terry1966, 23 January 2015 - 01:27 PM.