First off, use Max Weapons as your standard power setting. (Your shields will last longer when there are fewer things pounding on them. This is accomplished by destroying them quickly.)
That said, where are you having problems? It sounds like clearing out the Klingons from the first space map is the issue now. You'll have a long-ish ground segment, and then back to space for the finale..
It may be useful to identify the fixed defenses (turrets) and creep into their range and pick them off one by one, slowing down or coming to a complete stop if necessary to limit the number that can fire at you.
Other tactics depend on your selection of BOff powers.