This mission is easy, so only one comment is provided.
In most cases, it makes sense to destroy the enemy's Harvester (i.e. income) before assaulting their base, but in this mission, you have the real option of taking out the base first. This allows you to capture their Refinery intact while the Harvester is inside, which captures the Harvester as well. Now you have an income!
But when you accomplish this, you find that there is nothing left to fight, so it doesn't matter either way.