Yeah, based on that picture and the work I've done on 5th and 6th generation Accord suspensions, it should be the same...yes, that is the "upper ball joint". Is there anything other than the slack that makes you think that it's the UBJ? Have you had an alignment? Is the tire and wheel combo balanced? Does the boot on the UBJ look damaged? Have you compared the other side of the car to see if it has the same movement? The ball joint will have some slack normally, that's what allows the knuckle to go up and down while keeping the wheel/tire relatively vertical.

If it IS the UBJ, then you would remove the cotter pin and castle nut on the bottom of the bolt part of the UBJ, release the ball joint (it is wedged into the upper A-arm). This can be done by either just tapping the arm, using a pickle fork type ball joint remover, or a combination of the two...or the preferred method is using a leverage screw type ball joint removal tool ($20 at local autoparts store) that won't damage the boot and you don't have to beat on stuff hoping it comes loose.

Then remove the A-arm or the extension that appears in that diagram, and then change the ball joint. Couple options here depending on your handiness. You can beat out the old one and tap in a new one or the easier method is to use a ball joint press to press out the old one and press in a new one ($15-20).

Luckily the UBJ isn't nearly as much of a pain to break loose as the LBJ on Accords.

Hope that helps.