it does come out the top. you may have to remove some items to acess it. you can get the socket for it from a parts store for a reasonable price. make sure you get a good quality replacement o2 sensor.
im not sure but my best answer would be if you can see it thats a plus, unbolting something simple as a coil pack to gain easier access to the sensor do it. my rule a thumb as a mechanic dont take anymore off than you half to. but where a person is doing themselves move a couple of things your not charging yourself by the hour!