I didn't go to any games, but my Dad was the airport manager at that time, and the N Koreans stayed at the airport hotel so he was involved to some extent. The N Koreans had the biggest delegation of any team at that World Cup. There were more security people than players, by some way. There was some concern that there would be demonstrations against the players (the Korean War was only 12 years before), but there was no hostility at all. The players did some training at the airport on the football field there, with an army of security people round the pitch. There was also a well publicised trip to the Oak Tree pub, where they were given beer (I don't think they liked it), accompanied by their chaperones.
The N Koreans played all three group games at Ayresome Park, but the crowds were pretty poor - just 16K or so I think.
My Dad reckoned the huge security presence was to stop the players from defecting, especially after the win over Italy. The team set off for Liverpool to play the quarter final against Portugal, and I think they were intending to stay on at the airport hotel. The logistics were just too difficult though, and they had to stay somewhere in Liverpool, presenting their minders with a huge headache because they couldn't secure the place.
Anyway, they lost, and the story is consigned to history.