Years ago, I had an electrician install inline turbine fans to replace the very noisy original NuTone fans that most houses have. They move twice the air, and the only noise is the airflow. The turbines mount on the rafters, several feet of flexy hose from the original fan box duct (you don’t have to put a new vent in the ceiling.) It cost more than the original junk, but after 20 years, it’s still worth every penny. Inquire at your local electrical supply store.
not particularly difficult. Before you do this take the old one apart. Make sure it’s disconnected. You can have 2 power sources going to it if it has a light and it’s set up on 2 switches.
most older models are serviceable. take the motor out and give it a little oil. DO NOT USE WD-40 on the motor. I did this a year ago by accident and the fan lasted a month before it bound up. WTH? hunted down the oil can and discovered it looked EXACTLY like the 3in1 oil I usually used. Bastards. Took it down again and cleaned the bearings and then used real oil. Works like a charm and will probably run another 20 years before servicing.