I am thinking of buying 1999 mercury cougar auto trans V6, ad says needs gear postion sensor. Should I buy? IF YES HOW DO CHANGE GEAR POSITION SENSOR, HOW MUCH?

I have one of those cars and personally, would not recommend it to anyone period...same year, with the 2.5l v6 and auto, it just hit 103,000 miles and its poor quality car,front end shakes with new tires, had to replace rear hubs which are same as a Ford Contour(also junk) there are alot of similarities to the contour... took it off the road and replaced it with a 1997 civic 5 spd with 169,000 miles...problem solved