Doing my best to avoid a big hockey vs everything pissing match, here's my opinion on the issue:
In the short term, yes. If you don't spend money on one thing, you can spend that money on another. If the REA doesn't have a plan to spend excess reserves on upgrades and maintenance, it is supposed to return that money to UND.
In the long term, unclear. It's difficult to say how the behavior of hockey fans, who contribute the majority of outside revenue to the athletic department, is affected by the new video board. Are the fans more likely to increase donations? Are the fans more likely to pay UND more for tickets? Are associated businesses more likely to increase advertising spending? These things could all result in a net gain for the athletic department in the long run.