To access it, you'll likely need to:
1. Open the glove box.
2. Remove the glove box. This usually involves removing a few screws or clips. Consult your owner's manual for the exact procedure. Some models may have a release lever.
3. Locate the filter housing. It's typically a rectangular box behind the glove box.
4. Remove the filter cover. This might involve a few more clips or screws.
5. Replace the filter.
Important Note: Always consult your owner's manual for the specific instructions and diagrams for your particular 2003 Ford F-150 model. There are differences between different trim levels and configurations. The manual will provide the most accurate and safest method for accessing the cabin air filter.