It is difficult to give advice about teeth without knowing how bad they are. A good dentist is probably the best person for this.
I suggest keep your teeth as long as possible. Real teeth are better than false teeth. But the time may come when that is not an option.
I have some Amalgam fillings from back in the days when I believed that everything a dentist does for you, is good for you. As I need work done to the teeth involved, I will have the Amalgam replaced. I will not just have them all replaced immediately. I know others do that.