Is the digitizer on the motherboard?

We have 2 S3 phones with separate problems: one was in a pocket and suffered dampness while hiking, then the touchscreen went down. The other won't take a charge. Assuming damage at the motherboard. Wondering if I can swap motherboards and have one useable phone for the kids to have WIFI etc. (we moved onto new phones as plans were done, so this isn't a time sensitive).