At this point if a probe could just taste the plumes, it might be able to identify evidence of organic chemistry, heck maybe even be able to identify the vacuum-desiccated remnants of living organisms. We're decades away from building a probe that could actually bore through even a few kilometers of ice, but being able to build probes that could land on the surface and analyze the deposits left over from plumes should be well within current technical capabilities.
At the moment Europa really is one of our best shots at identifying life on another world. Even if Europa has never developed anything more complex than bacteria, being able to sample its DNA, or even cooler, finding some other system of protein encoding and heredity would literally be one of the most significant scientific discoveries in history. Just having life there, would go a long way to confirming the belief of many scientists that all life needs to get kickstarted is liquid water, organic compounds and energy.