The best way to get there imo is by RER train. The train station is located between the DLRP parks and the Disney Village. I beleive that it is one stop on the train and takes about 3 minutes (and you might be able to get on one of the really cool double decker trains).
We used it in 2004 and it was under 5 euros return for two adults and a very, very easy journey.
last march we went to val d'europe and valle village
we just went to concierge at our hotel and booked a direct shuttle bus which picked us up at 10am in front of the hotel and drove us to the entrance at valle village. the journey took only about 5mins and was pleasant.
if i remember correctly it was around 5euro per person including return
As you get off the train you turn left and exit by the stairs into the main part of the station.
In the main centre I think places worth a look are Sephora (fab cosmetics), Auchan supermarket, some of the clothes shops (look out for Gap, Springfield menswear, H&M plus some other places with different stuff), there is a home store very similar to Pier (halfway down on the left), also Jeff de Bruges chocolates yummy. Then at the far end you have the restaurants before heading out to the designer village bit.