I'd really like to see Stephen Baxter's Saturn mission. Could think of a better thing to do with the Shuttles and the old Saturns. For IS flight, I'm not so sure. Else it's hopeless. Also the radiation levels are real bad.
Neutrinos are the big worry.
Who knows how much damage they can do in quantity - and no shielding stops them. However toxins usually target certain hosts, and even more so for pathogens. Perhaps exobiological systems will use stereomolecules incompatible with ours, but beyond that I doubt there'll be a lot of transfer. Molecular homologies do arise between widely different species, but these are yet to be documented as causing disease. If you want some idea of exobiological contact think of deep-sea fishing and what they might dredge up.