2001 gmc Jimmy 4x4 problems

I have a 2001 gmc Jimmy with a 4 push button automatic 4wd system, it was stuck in auto 4wd for almost a year and then last week, it started jumping from 2wd to 4hi. while driving it will change. Then this week all the lights on the dash went out and the truck got stuck in 4lo. went from 25miles per hour to 2 miles per. I got it home and had "someone" come check it out. He replaced the fuse and got it back in 4hi. then he checked the transfer case and said he thinks it gone bad, so he disconnected the motor. now when we got it back it was still in 4hi, yesterday it changed to 2wd again and its stayed and i heard and felt the truck engage, so if the motor is not hooked up how is it still engaging and does this sound like the module to anyone and not the transfer case itself? before i spend the 200.00 to replace the transfer case should i replace the module? HELP?