Transmission problem
2002 Mitsubishi Montero 6 cyl All Wheel Drive Automatic 101645 miles

My Montero has a manual shift lever to the transfer case that refuses to budge. I am currently sitting in AWD, but have no ability to shift up to 4hi or 4lo. I was able to move up to true 4 wheel drive for a couple of weeks after I got the car, but even then it was an ordeal getting it to engage. I was required to hold the lever in place until it "took over" and was able to run in 4hi. 4lo was always a crap shoot. Any ideas as to what the repair would be and cost?

Thanks
-Cameron