To upgrade starbases, just send additional constructors to them.

The module you have available is most likely the one that gives +1 to all three attacks, because this is unlocked very early in the hull research line. This module is a prereq for quite a few others, so expect to see 6 or more modules available after you upgrade.

The other possibility is a sensor range upgrade, as all you need for that is Sensors I.

IIRC, you do get some nominal amount back.  In my current game, I just flipped a planet and decommissioned the influence bases I had built around it and got 40 BCs fo9r each.  One had no extra modules and one had a 25% bonus module on it.

I do not know if one gets money back for destroying mining bases or asteroid field mining facilities.  It would be simple to test, but I won't be able to game until late today at the earliest.

One point to consider is that, after the first few non-mining bases, each successive base costs more and more.  Thus, even if you get ~0 back, destroying no longer needed bases reduces the cost of the next one you build.

Oh - and yes, they cannot be moved.

Are you asserting game logic in the same game as the DA MCC?

Thanks Guys.