Hmmm, odd...
The main zip file for the Discus is duo_xv1d... when you unzip that you'll get two folders named DUO_DISCUS_X_(Front)_WINDE and DUO_DISCUS_X_(Rear)_WINDE.
Dive on into the "Front" folder... find the Gauges folder, now you should find a whole pile of .gau files - copy them all into your main FS9 gauge folder. There should be:
mr-yawstring.gau
mr-fs9-caiset.gau
mr-asw28.gau
MR.TR-010.gau
MR.SP-005.gau
mr.sch-004b.gau
autcrd1.gau
asw20bl.gear.gau
Just for those without pedals, the autcrd1.gau is an auto-coordination gauge that allows you to fly using the stick only should you wish (without that awful arcade style numbness that the default FS9 "auto-rudder" feature has).
mr-fs9-caiset is a working replica of a Cambridge Aero Instruments GPS, electric variometer, altimeter and glide computer. To switch it on, place your mouse over the knob/button (its at about the 11 o'clock position on the face of the instrument) and click it to the right... the screen should turn on and you may hear some beeping (its also a functional volume control for the audio vario).
Once its on, use the "up" and "down" buttons to change the display. I prefer the altimeter readout at the bottom, two vario displays top center and the push/pull adviser at top left.
You'll see another instrument that looks similar. This is the actual GPS part. I'll send the two of you a PM with the Central North Is. waypoints in it so you can actually use it (the default .dat file is for the Wasserkrupe region in Germany).
Sorted? Sweet!

Since I dont instruct in real life any more, I may as well have a crack at it here haha