I believe you get the lightsaber on the 5th level or so. But you shouldn't rush it, as soon as you get it, you likely won't use any other weapon again. Haven't played the game for an extremely long time, but it is really good, pretty interesting story that gets a lot better near the end. I'd have to recommend you get the sequel, Jedi Academy as well, though it's quite a bit different.
And even though it's not a very similiar game I'll agree with the second poster, Knights of the Old Republic is the best series of Star Wars games ever, and shouldn't be missed by anyone. I'll have to stress though, that it is an RPG, and does have more dialogue scenes that actual combat.