Yes, you can replace the bearings and the seal in the nose. You can buy the two bearings and a seal from places like ZZP or rollingperformance.com. You will need a press to remove the gear from the shaft to change the inner pulley. I'm sure a machine shop can do it for you for a reasonable price. rollingperformance.com has a how to for doing this. Your bearings may not be shot though. If it sounds like rocks tumbling, then it is probably the supercharger coupler. That can also be bought from the same sites mentioned above.
As far as the cooling system goes, have you checked to make sure the temp spikes are real or could it be a short in the wiring on the temp sensor? If it's real, then I would flush the entire cooling system and refill it. Make sure you bleed all the the air out when done.
The blower not working on any setting except 5 is 99% of the time the blower resistor. It is located under the passenger side of the dash right against the firewall behind the blower.