To colonize or seed life you don't need to launch huge space vehicles with enough life support to maintain a breeding population, though. You can just launch some kind of self-replicating microbes capable of directing themselves into the forms of life you want to encourage over time. The precise ability to do this would depend on your current state of technology, but we're pretty close to developing full blown synthetic biology and genetic engineering ourselves, so it's hard to imagine they'd need to be more than a few hundred years more advanced than us at most. Microbes can be engineered to be immune to most dangers from space travel as well, similar to tardigrades.
To head off the common rebuttal of "maybe they wouldn't have any interest in it," with more advanced technology smaller and smaller groups of individuals would be capable of instituting such a project, to the point where any high school kid with a synthetic biology kit and some toy rocketry kits could colonize the entire universe (owing to relativistic effects). You'd have to assume their society underwent some kind of massive convergence of social norms away from any individuality such that no few members of their species ever had both the capability and desire.
By the same logic, any depressed high school kid could also engineer a pathogen to wipe out their entire civilization before that happened. (I think this is a plausible great filter candidate)
You seem to be assuming a notion of continual human progress. In a few hundred years, we'll probably be in another Dark Age, judging by current trends. We're like the Roman Empire in 200 AD.
Progress is the exception, not the rule, so far in human history.
This might work on a baron world, but any place with a developed ecosystem would likely see these things out competed very quickly do to the massive overhead of needing to survive in space for a long time.
Or they would be engineered with huge advantages against an ecosystem which had never adapted defenses to them (typical of successful invasive species on Earth), and work on timescales much faster than typical evolutionary ones. These would basically be microscopic von Neumann probes, presumably with some kind of self-organizing emergent AI to direct their progress, not just spraying random bacteria everywhere and hoping for the best.
Only a tiny fraction of species end up as invasive, because the local ecosystem tends to be better adapted. As to ‘grey goo’ there is fairly good evidence that’s far less possible than you might think.
If you don’t stick with Hydrogen Carbon Nitrogen Oxygen you’re going to have a much harder time finding what you need to grow on earth. For extra solar stuff even those might be hard to find.
If you do stick with HCNO it's hard to get a leg up on nature without simply making a few minor improvements which has limited value outside specific situations. There are also a lot of tradeoffs with binding energy etc.
To head off the common rebuttal of "maybe they wouldn't have any interest in it," with more advanced technology smaller and smaller groups of individuals would be capable of instituting such a project, to the point where any high school kid with a synthetic biology kit and some toy rocketry kits could colonize the entire universe (owing to relativistic effects). You'd have to assume their society underwent some kind of massive convergence of social norms away from any individuality such that no few members of their species ever had both the capability and desire.
The entire plan is mostly laid out by: http://www.tedxvienna.at/watch/why-aim-for-the-stars-when-th...