The picture I posted is the inside of the printer, to the right hand side. You can see the carriage rod (the silver bar) in the upper part of the picture. I no longer have an Officejet 6500 here, but my recollection is that this area is covered by a black plastic guard in the Officejet 6500. This would make it more difficult to replace the part.
For the Officejet 6500 the printhead is removable, I would suggest just discarding the brush. Keep an eye on the print quality, if you get any sign of black ink smearing you can remove the printhead and clean it with a damp Q-tip or soak it as described in this post.