Clean ever connection with a soft toothbrush. As well clean the logic board use a 99% isopropal alcohol for all cleaning. now is the time to start drying out the phone. Set the screen in a desiccant or silica gel leave it in for several day moving it from time to time to get the max effect from the desiccant . use a blow dryer on a low heat setting to dry the rest of the phone. replace the battery with a new one consider the old ones done. Clean again with isopropal alcohol let dry and when you think everything is clean and dry reassemble the phone (make sure to clean the contacts on the screen after removing from the desiccant). Once you've reassembled the phone its time to power it on. Hold your breath and hope for the best