We will be in Paris in two weeks. We would like to tour both the interior of Notre Dame and Ste. Chapelle. Is there one tour that does both or are separate tours recommended?
You can self tour both sights yourself.
For Notre Dame there is no admission fee as this is a functioning house of worship. If you are unable to secure tickets in advance, don't worry. You can join the line for unreserved admission when you arrive. It generally moves fairly quickly. For the best experience, try to reserve or get in line early in the day before the Cathedral becomes too crowded. You can also attend a service at Notre Dame without reservations.
You can rent an audioguide or reference a good guidebook (like Rick Steves' Paris) while touring the Cathedral.
For Sainte-Chapelle reservations are required. An audioguide can be rented. In addition, the upper chapel also has descriptive boards in several languages describing the stained glass windows.
Plan on spending extra time for the security check in advance of you're entry to Sainte-Chapelle.