Got it. (And in the fall, often a lot of MVCI's have 35-40% room rate sales, so keep checking. The Paris Disneyland MVCI is sometimes 140-160€/night, maybe even less.)
There are 3 options (4 if you want to walk it, and ya, it would probably take about an hour, as I think it's 3 miles from Disney.)
3. You can taxi, but it's about 18€ one way, plus about 1€ a piece for luggage.
You can click on the images to enlarge.
It probably takes about an hour to train from Paris Disney (you want the RER A, red line, straight shot) to La Defense. Again, if you have the Paris Visite zone 1-5 pass, the train, the bus, the Paris metro, and the RER B train (RER blue line) to/from CDG is all inclusive.
Link back to original discussion that prompted this thread, as the original discussion (about Italy) also has some excellent information on Paris Disneyland, Renaissance La Defense, and Paris in General (sometimes we tend to get "off track" ).