where is the heater core in the 1998 chevrolet malibu?

Hey dre. I couldn't find confirmation on the web but in most instances the core is close to the firewall on the passenger side of the car. If you are going to tinker with the heater core you should have a copy of your car's Chilton's manual handy. You will probably be able to find it at your local library but if not you can check your local book store or parts place. That should lead you to the core and give you step-by-step instructions as to how to replace it. You could also ask at the place where you get the new heater core. They will be able to give you an idea of the scope of the job. It's not fun and will require contortionist skills and, in most cases, removal of much of the dashboard. It's not a cheap job, but what price would you put on your sanity? Good luck!