Hehehehehe, Ill try and answer this one, without being too biased (Lol)
There are a few differences with the EF Series 1 and the Series II,
Most notable ones are.
EF Series I Fairmont Ghia -
Leather Trimmed Seats, with Velour Inserts.
No Chrome Door Handles
No Passenger Airbag
No XR6 Motor
No Ghia Badges on Door Trims
the EF Series II had
Full Leather Seats
Chrome Door Handles
Drivers and Passengers Airbag
Externally, you can tell the difference between the 2 by the following
EF Series 1 Ghia's had the same grille as the Fairmonts
EF Series 2 Ghia's had a chrome lip, with a Black (Not Charcoal) Grill
The Series 2 Had Gold Lettering for the "4.0i - Computer Torque Control" Badging on the doors.
Also Series 2 had the Words "Ghia" not the Ghia Crown Badge, on the Back and sides.
As for problems, the Ghia's are prone to the same problems as the Falcons, and Tickford Models.
Things to watch out for include
Head Gasket Problems
Airconditioning Compressor Problems
Power Window Motors Winding very slowly / not working
Suspension (Shocks in particular) do not match the Power Output of the XR6 motor, and WILL NEED to be UPGRADED ! (standard shocks wear out quickly !)
Transmissions are EXPENSIVE to repair, so make sure that the transmission does not slip, or is too harsh.
Hmmmmm, I think that is about it !