You mostly will splice wires...
The following wires can be spliced from the non-digital DIC:
Left Door
Right Door
Rear-Left Door (if 4dr)
Rear-Right Door (if 4dr)
Trunk
Washer Fluid
Dimmer
If not a few more (it's been a while)
You'll have to wire into the VSS line to pull the Speed Data for the millage/oil/etc.
Search on Google for: Digital DIC conversion Grand Prix
I believe AutomotiveForums has the diagrams still:
http://www.automotiveforums.com/t765...onversion.html