Replaced the screen on phone now the speaker doesnt work.

So replaced the screen on my iphone 3g, (must say rather impressed with myself as never done anything like that before) Put it back together and now the ear speaker wont work, if somebody rings me they can hear me but i cant hear them, odd thing is though it works if i put it on loudspeaker. Does anybody have any suggestions please. Please be aware that im new to all this so very descriptive answers would be helpful many thanks.

Oh yeah and also i think the flex cable is not fuctiontioning properly, i have a new flex cable, how easy is this to repalce.