Momentum is important, and it can help a team get to the finish line. Momentum will help psychologically propel the Rangers to the finish line. Winning is a confidence booster, and nothing is better for getting a team through the rough and tumble of a hockey game. They will probably get the cup.
I definitely believe that the game 7 win gave them a confidence boast that will possibly carry on into their next series. Their a great team, as long as they stay focus and continue to believe in themselves anything is possible. They just have to go into the next game with that mindset.
Since the Rangers beat the Capitals in the seventh game of the second round of the Stanley Cup playoffs, the question of will they go the distance remains. Te Rangers have traditionally shown themselves to be a team that rides waves of momentum such as the one they are riding right now post-victory over the Capitals. The Rangers may just skate away with another Stanley Cup.
It takes more then momentum to win and I don't think it is a very big factor. Momentum can always be stopped. It takes skill, a bit of luck and the other team having a worse day then you are to win. Momentum can give confidence to a team but not much more then that.