I saw this question last night, but I headed to bed before I could answer. I wanted to make it clear that, while the Romans did many things, teaching slaves to fight was actually something that scared them, too. One of the greatest nightmares of Rome was for their slaves to turn upon their masters - something that seems common for slave owners, really. However, I did want to make something clear - the very rare occasions when the Romans used slaves in the military (after Canae and Teutoberg, for example), it was in the case of a national emergency - and they weren't "legions," so much as they were "auxiliary troops." No, the legions were proudly Roman citizens - and no slave would be a part of them.

Now, as to the question on whether the Servile Wars changed Rome's stance on gladiators - it really didn't. Remember that, although the vast majority of gladiators were slaves, there were a not-insignificant number of Roman citizens and free men (and even some women!) who became gladiators themselves for the fame and fortune that it would bring. However, stricter laws against gladiators were enacted - most famously, there were laws against having more than a certain number of gladiators in one place, which played logistical hell with massive gladiator tournaments that big names liked to hold in Rome - but made it extremely difficult for them to revolt. Interestingly enough, for the wars against the Cimbri and the Teutones (ca. 105 BCE), Caius Marius took the army that had been trained by Rutilius Rufus during his (Rufus') consulship. When training that army, as they were also taken from Rome's poorest citizens, Rufus had brought in a gladiatorial trainer to teach them weapons handling. The techniques that were used in that training programme were then adopted by the Roman army for the next few centuries.

Hope that helped a bit :) If you're interested in Spartacus, I highly recommend checking out Barry Strauss' The Spartacus War. If you're interested in more on the Roman legions, a fantastic book is Adrian Goldsworthy's The Roman Army at War. If you're interested in the leaders of the Roman army and how they shaped Rome herself, check out Goldsworthy's In the Name of Rome. I used knowledge from all of the above to form my answer :)