2002 O/D Light Flashing

My 2002 XLT O/D light flashes after about 15 min of driving. 4x4 High and Low does not engage. Transmission seems to be OK although vehicle has 97,000 miles on it. Someone suggested a possible Torque Converter Clutch Selonoid problem. Does this sound likely? Cost? Is it something I can replace with moderate automotive skills.

TNX