Might be better posting in the networking forum for an answer to the file sharing query.
I understand that a VGA splitter is to allow one PC to display on multiple monitors - not sure if it would work as you need. What you are more lilely to require to share a monitor is a KVM switch. This will allow two (or more) PCs to be controlled by one keyboard, mouse and monitor. Each PC will display on the single moitor when switched.