Auto Transmission problems

I am having trouble with the tranny on my 1998 Ford Contour (4cyl.) 145,000 miles. The overdrive no longer engages. The overdrive light continually blinks. The transmission shifts hard from first to second and sometimes just slips and spins revving the motor and losing momentum. The problem has been slowly escalating over the past several months, but seemed to fully present itself "suddenly" about six weeks ago. The car is still being deriven although it has also developed an additional problem of stalling. Please help.