There is a shift cable connecting the shifter to the tranny, and yes, when it breaks it will allow the shifter to go any way you move it. Also, shift cables aren't too expensive, but the amount of labor to put one in (Depending on the car) will be close to 4-500 bucks. This ofcourse varies on the $$$/hour labor rate the shop you take your car to is at. Most shops are somewhere around the 60-100 bucks per hour of work these days.
1999 Chevrolet Camaro SS (PC'd)
1994 Chevrolet Beretta Z26 Q4 (W41 M90'd)
2004 Chevrolet Silverado 2500 (4WD)
My wife's cars:
1971 Dodge Charger SE (stock and original 383 auto)
2004 Subaru Impreza WRX (kid-hauler)