Dexcool works just fine as long as you don't let your coolant get low AND you have a pressurized coolant reservior with the pressure cap on the reservior. Which the Grand Am does have a pressurized reservior. The problem with Dexcool is it doesn't tolerate air in the system, so if your coolant gets much below the full level or you have the pressure cap on the radiator and not on the reservior then it will oxidize and gum up, and even worse if you have an all iron engine. It is also not compatible with certain plastics, but that wasn't the primary reason for the LIM gasket problems.
Dexcool is compatible with other types of anti-freeze, including green. So you could go on using Dexcool and get extended protection or you could switch to some other extended life coolant. You could even put the green type in, but I don't think it would be a good idea because you'd get less protection and have more frequent change intervals. Dexcool in addition to protecting longer protects aluminum better and is silicon free so there's less water pump seal wear. That may not be the case with some other types of extended life anti-freeze, but green works well so I imagine other extended life anti-freeze works good enough too.