I have a 17 year old Trne Furnace and the blower motor hums all the time. The ac unit was replaced a couple of years ago, not sure if the hum started back then

You say humming,Is it just trying to run or is it humming while it runs
If its not running at all ,you either need a capicitor or the motor is bad

Seems to be running OK, just humming when off. Not sure if I'am getting the same air flow that I used to the house doesn't seem to cool or heat as well as it did.

Blower motor has a tiny port on the top, tiny metal port comes out by hand the size of a pencil eraser and sometimes smaller. Anyway pull that little port off and drip some motor oil in it not much about a half a tea spoon. If you can't find this oil port call a repair man and say that the blower fan bearings need oiled , repair is about 100$ to come out and oil motor . If you have a sealed blower motor you will have to replace whole motor , parts plus labor will be around 3-400$.