Most definitely the highlight of a trip to the DPRK. It's spectacular on an epic proportion. Thousands of participants, mainly volunteers & allegedly only about 10% are professional singers & dancers.
Seat prices vary but even from the cheap seats you'd fail to be impressed.
There are a limited amount of relevant souvenirs available, ie t-shirts, posters & cds. You can even buy binoculars.
No restrictions on photography or filming in the stadium.