My buddy has a 90 or so olds 88 or something like that, wondering how hard is it to change the knock sensor, what tools and that sort of stuff?

Mushroom shaped gadget on the back of the block just above and around the corner from the oil filter. About 1.5 inches in diameter. Just unscrews after disconnecting the connector.

Probably a special socket available but I just use channel-lock pliers.

its not behind the crank pulley? he was telling me that it was behind the crank pulley? he doesnt really know much about cars, so i dont know where he got that from? or is that where you are talking about?

Well the knock sensor is "behind" the crank pulley. It is also around the "back" on the "side" of the block approximately below the #2 spark plug. The crank sensor is the one that is directly behind the crank pulley/balancer

k, i cant remember which one he said it was, ill double check with him. thanks for the info.