| I'd say it depends on what type of music you'll be playing and more importantly, where you'll be playing it.
If you're playing country and bluegrass music (and maybe others), especially in Nashville (duh) and around the south, you may be given an NN chart to read. It will be good to know how, no doubt. But to understand that, you'll need a bit of theory. You'll need to know the numerals, that F# is the VI in the key of A, for example.
But you'll more than likely have to deal with traditional notation before it even comes to that.
Forgive me if you have already played another instrument for a while and you know all this. But Nashville numbers apply to any harmonic instrument, not just bass.
And in any case, I 2nd Ed's suggestion to get a teacher. The DB is not a "teach yourself" kind of instrument. | 
