Hi SWeese,
Thank you for contacting InSinkErator.
If you want to replace the mounting gasket of your disposer, you would have to uninstall your disposer. If you want to replace the removable sound baffle of your disposer, you would just have to pull the baffle out from the sink hole opening.
I have included a link below on how to uninstall and reinstall our disposers.
http://www.insinkerator.com/en-US/S....
For your reference, the part number of the mounting gasket is MGK-00. This kit includes one standard mounting gasket and one deluxe mounting gasket. Please make sure to use the deluxe gasket for your Pro 77 disposer. As for the removable sound baffle, the part number of it is RSB-00.
You can purchase these items from retail outlets, plumbing supply houses and online stores. Below are also the links for the said accessories.
Mounting Gasket:
http://shop.insinkerator.com/p/insi....
Removable Sound Baffle:
http://shop.insinkerator.com/p/insi....
If you have questions, please do not hesitate to contact us through insinkeratorfeedback@emerson.com or call InSinkErator AnswerLine at 1 (800) 558-5700.
Thank you.
Sincerely,
Jerica