I have been riding a 1996 GT Outpost for twenty years. The one in the photo appears to be the same general vintage, but not the same year. In any event, the front chain rings ARE welded together, so you would need to replace the whole crankset. I just replaced mine with a 3-ring set made by Acer for $40, which included a 5-minute installation that saved me getting my hands dirty. The package includes the chainring set and the two cranks (arms that hold the pedals). You need some bike-specific tools to replace it, so it might be worth playing dumb and asking the bike shop mechanic to put it on for you.

Great bike, that GT Outpost. I have put hundreds of dollars into mine over the years only because I don't ever want to ride anything else!