Screaming, tapping, & whining? Sounds like you have .... liberals
.... trapped in your burner.
Time to tear that burner down & see what the deal is. First, make sure nothing is jammed in the fan ( unlikely something could get in there, but you never know - mice are crafty little bastards). Next I would get the motor off & see how the shaft spins by hand .... and if it spins good, find a way to power it up & let it run for a bit ( off the unit, of course). If that's all good, the only other thing it could be is the fuel pump like Freddy said. Both are easy fixes, but not very cheap.
And before you do any of that, check the bearings for oil holes & try several drops of oil down there first if it has them.