Is expiation sufficient for making up the Ramadan fast of 2004, given that he was unable to make it up due to a prolonged illness?

We ask Allah to grant you healing. If you break your fast in Ramadan based on the advice of a trustworthy doctor that fasting will affect your health, then there is no sin upon you. You must make up the days you missed if you are able to fast afterwards. Expiation (kaffarah) is not sufficient if you are able to make up the fasts. Since you began fasting in Ramadan, this indicates your ability to fast. Therefore, you must make up the fasts to the best of your ability, and expiation will not suffice as long as you are able to fast.