Smoke on the Water has is a really good bass line to it. Roger Glover really shows what you can do to make an interesting bass line out of a pretty simple simple song. And no - he never plays the signiture guitar riff and I don't think he goes below the 5th fret.
That said - you don't have to play all of his variatiions. If I needed to learn this quick I would learn the intro and chorus part. Then I would pick out one of his lines for the verse and repeat it 4 times for each verse and then learn one of his repititions for the solo and just repeat that 4 times during the solo as well.
If that's too much then I would just play the chord roots for the verse and solo and just learn the intro and chorus part.
Fun song
