1997 gtp

Is it hard to change the super charger pully.

No but you need a supercharger pulley puller and installation tool like at the link below.

Pulley Boys (http://www.pulleyboys.com/gms2pt.html)

Also, ZZP has them available for purchase and rent.

^^^Make sure you get one like that, and not a 2-3 prong puller (all that will do is dent the pulley).