When the paper has finished copying/printing, as it's being pushed into the bin, there is a loud noise... Almost like quacking. I'm wondering if it's the rollers in the back. But not sure. Can this be fixed and how???
It could be fixed, but probably not both cheap and easy.
Most horrible noises come from the print cartridge, which is easily replaced, but not cheap.
If it is not the print cartridge, it would likely be a gear that runs a roller. If that is the case, the part would be hard to find, but at least most likely cheap, but not simple to replace. You would have to get out some tools, find a service manual and proceed to tear the machine apart.
Youtube is a good place to find tear-down videos in absence of a Service manual (These are not easy to find).
So if you have a service agreement with Xerox, or if it is still a new machine or new Print cartridge, call Xerox to have them fix it.
If none of the last sentence is true, its likely to be a lot of work.