If you TRULY have genuine interest in the war and DMZ, go. If you just want the "oooh ahhh scary North Korea" stuff, skip it without JSA. The tunnel is literally just a tunnel you walk down and then have to walk all the way back up. The observatory and viewing area is cool, but it's still just simple Korean countryside. There's no "security theater."
I always recommend Tongin Market Lunchbox Cafe to try all the different kimchis and side dishes (don't eat like fried chicken and basic street food here). At other markets you have to buy a large quantity so the Lunchbox Cafe is ideal....can pick what you want. Get an empty tray and bag of coins. Item price varies in number of coins.
Also visit Ikseon-dong it's a "hot place" now with many cafes, food, and traditional atmosphere.