iphone 3g 16gb faulty ?

for sale is my iphone 3g in white 16 gb its recently had a new screen fitted and a back house for some reason since the back housing has been fitted the home button and mute button wont work the lock button tends to stick and it wont read my sim maybe and easy fix for some one who knows what they are doing looking for sensible offers in the worcester area sold as seen any questions feel free to email me many thanks