Here is link to the ITT-Jabsco model selection page. Select the model you have, then on that page select technical information. What you get is more or less an "Owner's Manual".
Do the maintenance procedures describes annually. And/or buy the "service kit" for your model, and install it as well ( each year ).
Mostly, disassemble the system, confirm that all flaps, duckbills are still well formed, pliable and smooth. Lube all sliding/rotating parts ( as described in manual ). Re-assemble, making sure that all connections are sealed and tight. ( Be careful when tightening a hose and clamp around a plastic fitting; they can crack! ) Check all electrical components for corrosion and correct as needed.
I would suggest: old clothes, gloves, Vap-o-rub on upper lip, and paper towels. Also, If you thoroughly flush the system with white vinegar -first-, you will greatly reduce the odor issue.
Mostly this is a lube and fix as needed project...