I’m not sure navigation would be that great a problem. If the ships were to wake up every hundred years or so and modify their trajectory towards the star most close to their direction of travel, they should progress reasonably well.
Some will be fooled by non stellar objects like galaxies and head in such an unhelpful direction, but most would tend to head towards real stars.
There are several tests that would prevent seeding on allready living planets. Most important of those would be to test for an atmosphere containing mostly CO2 and very little O2, and not seeding planets that have different atmospheres. The bacteria would create O2 in the atmosthere and fix Nitrogen into nitrates and nitrites making the planet more suitable for complex life forms to evolve.
The blue-green algae or Cyanobacteria is a photosynthesising bacteria info here Cyanobacteria - Wikipedia
I think I agree with Der Trihs the most.
Once we figure out how to make consciousness (which extends to pretty much everything with a brain, in varying degrees) actually pleasant. THEN we can spread its miracle to all the Universe. Then we can create life simply for the purpose that it may experience it. Indeed, it will be the definition of evil if we do not.
However, we actually have figured out how to make consciousness pleasant. With drugs and electrostimulation (I don’t mean computer interfaces, just plain old currents), and those are just the crude, old-fashioned techniques. That is no longer our real goal.
The real concern is that we are sooner to be crushed under the weight of our discovery than we can spread its joy elsewhere.
Therefore, Der Tihris, it may be wise to spread the pitiful, wretched life as the history of the planet has known it. So that should we fail (and God knows the odds are against us), we will leave descendends who may have another chance at erecting Heaven.
Ha, it sounds like I’ve let forth a load of crap. However, I think the universe permits only two philosophies. Nihilism, which says that suffering and joy do not matter. And mine, which maintains that they do and carries the idea to its ultimate conclusion. I do not see how there could be anything in between, a juxtraposition of consciousness mattering and at the same time not.