Passenger side door lock ?

Have a Nissan Sentra GXE - 1995.

The Passenger side door cannot be locked from outside nor can it be opened from the outside thru the key. You would need to lock and unlock it from inside to operate it properly.

any ideas as to how to resolve this issue ??
Do not want to spend money on this one (except for the parts:)
would like to do it myself...