1998 olds bravada smart trac 4 wheel drive



4 wheel drive would not engage replaced encoder motor,then vehicle stuck itself in 4 wheel drive was told by dealer that the transfer case control module needed to be replaced,so we had it replaced did not solve problem. the vehicle 4 wheel drive system is locked in and will not come out of 4 wheel drive,we can lock and unlock by applying ground and power at encoder motor circuit,but as soon as vehicle slips on snow or ice it locks back into 4 wheel drive and will not come out of 4 wheel drive.dealer now saying transfer case clutch assembly may be a problem need to disasemble the transfer case and inspect, is this a tough job and how long does it take to open transfer case and inspect,also what else could cause the 4 wheel drive system to stick in 4 wheel drive like this?