Oh yes, at $120, it is most definitely worth it. Especially since your DS lite is old, and they were $120 when released. Snag a copy of Ocarina of Time 3D, and you'll be set until Christmas time. Once games like that Super Mario Bros 3D, and Starfox 3D come out, you won't regret buying the 3DS. What most people don't realize, is that the 3D on the 3DS is not a gimmick, and is actually quite impressive. ESPECIALLY for a handheld. I'd say it's better than 3D TV's, in my honest opinion. I mean, they have a better viewing angle, but the 3D on the 3DS takes the cake.
Buy one. Also, if you need any more info, let me know.