Overdrive Highway RPM's
 

Just picked up 2000 Sable from father-in-law, drove it home from Dallas to Houston. At highway speeds, 70-75, rpm's are at 2500-3000 as if transmission is not shifting into OD. Is this normal rpm range for the 24V v-6 engine and transmission?

It has 69k miles on it. It also is howling very loud and can feel it in the gas pedal. Is this going to be a wheel bearing, cv shaft or transmission issue?

There should be an O/D on-off switch on the gearshift knob which you can toggle and see if the RPM changes.
Wheel bearings will howl and change pitch or dissapear as you corner or taking turns, changing the load on the bearing. The CV joints will make a clicking noise, changing as you do cornering.