You can do upper ball joints for far less than $400. You should be able to do it under $100, more if you get if aligned. To test it get the car in the air and grab the top and bottom of the wheel and see if it moves. If it does, its a ball joint, have somebody look to see which one. They are not all that difficult to change, I will be changing mine soon. BTW, Ford OE parts are not any better than a TRW part at Advance, the OE ones actually say TRW on them. They come with a lifetime warrantee whereas the Ford ones won't.