Out Door Paul,
The selector lever mechanism is a real pain to get to. The best way of dealing with it is remove the centre console and foam gator. Under that there is a rubber gator that is rivited to the body. You will have to drill out the rivets to get it off. They can be replaced with self tapping screws if you dont have a pop rivetor to replace them.
Once off you will be able to see a bar that runs left to right and is connected directly to the transfer box lever. You will have to use loads of WD40 and keep working it loose. Once you have freed it up I suggest using some white greese to prevent it jamin up again.
You may be able to squeeze round the side of the transfer box from underneath but it will be hit and miss with the WD40.
Hope this helps.
Craig