No tricks to share other than the cap outside may have separated from the cap inside and it make take some effort to remove.
Seek a local shop's help near you if needed.
Use this link to find some shops near you that can help with your concern:
www.repairpal.com/repair-shops
RepairPal Certified shops can diagnose and repair your 2000 Saturn LS2. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.