Maybe.
Since no person or piece of software is truly clairvoyant, I would take the results with a grain of salt, especially the whole Norton Security bit. All that could possibly mean is that Norton Security didn't detect a virus that it's reporting. Doesn't mean you don't have something malicious, just that Norton Security hasn't reported it.
The 30°C is probably correct. There should be a sensor on your hard drive, and more than likely your piece of software read the sensor and reported the value correctly, but as for predicting the future lifespan of your hard drive, "Reply hazy, try again."
For the virus and malicious part, should I do a quickscan of my computer for anything malicious or any virus?
As for the 100% health condition? Here's an analogy: A 10 year old and an 80 year old could both be in 100% health, yet we can't guarantee either will be around tomorrow. Statistically however, the 80 year old does not have as long of a life expectancy, does he? So, what does a 100% health report really mean?