The last shifter assembly that I have removed was one from an auto. Similar, might be different though. Basically, once that you have all that interior stuff out of the way (the plastic skeleton can be tricky to get out without destroying it!), and you have the cables out, it just un bolted and came out.
The auto is definatly different though, probably not as complicated as a manual trans might be. We just cut the shift interlock cable at the front (we are converting auto to 5 speed) and then disconnected the shift cable and pulled it through the firewall. 4 nuts I believe and then it came out.
Is the shifter assembly in the car different for the getrags compared to the isuzu's? I would think that all 4 speed ones and that all 5 speed ones are the same. What commonly needs to be repaired on them too? My coupe has over 225,000 miles on it and I notice no sloppyness or weirdness; is there some common occurance that I have not yet experienced that I haven't yet?