PS - A good way to check ball joints: Carefully jack the wheel up with the jack under the end of the bottom suspension arm. This will remove the weight of the car from the ball jint. Jacking the car up any other way will allow the suspension to fully extend (upper arm hits the top-out bumper) and still allow the spring to put force on the lower ball joint. Once the wheel is jacked up and the tension is relieved you can try wiggling the wheel bottom in and out. With no pressure on it a worn balljoint will clunk around and be noticably slack. Under tension the worn ball is pulled firmly into the socket and won't clunk until it breaks totally free.

Other warning signs: Torn or dry rotted boots, squeaking.

PS - Use the above method to replace them to. Thankfully on an 1800 they bolt on and aren't hard to replace at all.