When would I know to get a new blower motor or resistor? I feel my fan isn't blowing up to what it should be. The recycle is probably the most powerful, with the high setting.. Not so high.

 

The resistor just gives you different fan speeds, when it goes the fan speed defaults to high. The blower motor is pretty easy to remove to inspect if fan is spinning freely, also you can weasel your hand in there and dig out any debris that maybe restricting flow.

 

Have you searched for "wild vents", you may just have a vacuum problem not moving the doors like they should move.