Sorry I had to stop because of classes, last semester was Intro to C++ and the next two semesters is Math for Game Programming with C++ Labs, so its been difficult.
I was thinking about how to modify the sign to accept new hardware since the sign is so obsolete, There is a EEPROM that controlls the sign, a 27C256, I looked up the pinout of this chip and it has A0 - A14 and D0 - D7, it aslo has /0E, /CE, Vpp, Vcc and ground. On a Mega board you have the same outputs as well, So couldnt you pull the EEPROM, jump in wires corresponding to each one, basically turning the Arduino into the EEPROM? The EEPROM is where the program for the sign is held anyways, the memory chips is the buffer as far as I can tell. If this will work, I can add to the Arduino board a better way to communicate with it.