Hi,
Another approach is to simply use two sentences, and thus avoid this punctuation problem. This will also make it a little easier for the reader to see your meaning.
We need to make changes. These are to come in three areas of our operation: operational, administrative and financial.
By the way, it's not great style to say you are going to make changes in the operational area of your operation.![Smile [:)]](/emoticons/emotion-1.gif)
Best wishes, Clive