First off, when I switch the fan from heat to vent, or from heat to defrost (just examples), it will take a good 10 minutes to switch.

Second thing, my heat and AC only works on high. The rest of the speeds only blow low air.

Are these related? Will I need a new blower motor or a resistor pack?
Any advice is much appreciated!

 

Not sure what u mean when u say "switch the fan from heat to vent". The fan is all by itself regardless of where the vent selector is positioned and regardless of where the temp selector is set. The vent selector is all by itself regardless of fan speed and regardless of where the temp selector is set. Heat can be added to any vent position, including a/c, by moving the temp control. Vent selector is vacuum operated....check for/trace down vacuum leaks. Sounds like a new fan switch is in order to control fan speeds.