To find the fuel filter, you should:
1. Check your owner's manual: This is the best place to start. The manual will have a diagram showing the location.
2. Look online: Search for "[Your Engine Type] 1998 Dodge 2500 fuel filter location" on Google Images or YouTube. Pictures and videos are incredibly helpful.
3. Look near the fuel tank: This is a common location for fuel filters, but the exact placement varies.
4. Look along the frame rail: Sometimes the filter is mounted to the frame rail near the fuel tank.
Without knowing the engine type, I can't give you a precise location. Providing the engine details will significantly improve the accuracy of the answer.