This article calculates the odds for Earth ejecta seeding Europa (actually, just Jupiter, but some would hit Europa).
A frequent topic here is the ability of comets and wet asteroids to serve as vectors for replicators, given that a) they have liquid water, b) organic compounds like amino acids and nucleobases, and c) small gravity wells that are easily escaped. Some comets are hyperbolic, which means they escape the solar system. (See here for calculation of spread rates between solar systems based on hyperbolic comets.) Whether this is the seedign of proto-biological materials, or a "lifecloud", or von Neumann probes is really up to your ability to gauge the intentions of probe designers, their ability to prevent function-destroying but fertility-enhancing mutations, and your own cut-off for a definition of primitive life (self-replicating RNA? Viruses? Floridians?)