Don't be confused: a dead blower motor may move a tiny amount of air at highway speeds. But if you're changing the fan speeds and getting no more/less air, then you may very well have a dead motor.
To test your maxifuses, grab a multimeter and check for voltage at the blower motor connector. If there is no voltage present, then you have an easier repair; it means that a maxifuse or a relay is kaput.
Otherwise, your blower motor is that bump in the center of your firewall. There'* a fragile plastic cover and vacuum hose over it. A little ratchet work will get everything in and out. You may have to loosen a bracket and remove the strut tower bar if you don't have tiny hands. I did this repair on mine; it'* easy, but you may have to struggle with it (at the GM plant, I think the blower went in before the engine).
2007 Pontiac G5
1999 Pontiac Grand Prix GT - Stock engine ate transmission.
1997 Pontiac Bonneville SE - Cammed engine ate transmission.