Open Europe have provided a comparison of the Lisbon Treaty and the EU Constitution here. It circumvents the fact that the original Treaty is in French and only shows the modifications to the two founding Treaties. There is also a guide.
In short, David Cameron’s response to the Treaty holds true.
I suggest that the correct action is to insist that your MP demands a referendum: www.writetothem.com.
Now is the time. If we refuse to ratify, we are in strong position; a government withdrawing following ratification would face the most difficult and uncertain problems.