George William Herbert wrote:

Given any reasonable set of assumptions for evolving
technology levels, a single source planet will probably
directly colonize a large fraction of a galaxy.  Some of
the factors related to how far you ultimately could
directly launch colony missions are unclear... but thousands
of light years may well be possible.

But the odds are high that it just takes one successful
world with one successful launch system...


-george william herbert

Even with the engineering and motivation as a given, there are many possible
snags.

You might discover that you have zero resistance to local bacteria and
viruses. Or the local forms of life have no resistance to your bugs, and
they kill what you need to eat because your crops don't survive the local
soil.

-- 
Tony Sivori