The first stage is to orbit a cubesat, a tiny, coffee can sized satellite that would contain two highly accurate accelerometers that would go into orbit around Europa and measure its gravity field. In this way the location of Europa's subsurface oceans would be mapped. Indeed it is possible that the probe might find an opening through the ice crust to the ocean, warmed it is thought by tidal forces.
The second stage is to deploy even smaller probes called chipsats, tiny devices that contain sensors, a microchip, and an antenna. Hundreds of these probes, the size of human fingernails, would float down on Europa's atmosphere to be scattered about its surface. While some might be lost, enough will land over a wide enough area to do an extensive chemical analysis of the surface of Europa, which would then be transmitted to the cubesat mothership and then beamed to Earth.