Yes, take him seriously, he's not too young to train, and kudos to you for taking note of his interest! You're not pushing when he's interested and ready to try. Like Dana K said, prior to disposable diapers (and Pull-ups) the average age a child was trained by was 18 months. My little guy was interested at around 21 months, but I thought "He's too young" and missed my window of opportunity. He's currently 27 months, and we've been training about 5 weeks (with a 2-week lull due to his flat-out refusal to try) and he's doing good, though we hit some rough patches because he'd gotten more set in his ways.
We use a potty chair, but I have a toilet insert for when he's ready to sit up on the toilet. My grandson trained recently on a toilet insert, mom didn't want to train him twice, do what works for you.
Get him in cloth training pants and plastic pants, diapers keep them too dry so they don't have an incentive not to go in them, and transition to regular underwear once he's going regularly on the potty.