Hi
I have a GM-8 without Gemini that I use as my field setup, to autoguide, all you need is the Shoestring Astronomy GPUSB and a 14ft flat cable:
http://www.store.shoestringastronomy...roducts_gp.htm
Simply order them direct from Shoestring Astronomy.
GuideDog is getting a bit old now, I would suggest you try either PHD or GuideMaster (both free). Just make sure you run the Guide Rate at 0.5x or the mount will start to occilate and chase the seeing.
You dont say what you are using as an autoguider as some of the newer guiders have a direct connection to the autoguider port and don't need any adapters.
Cheers