I was in the same position! Until our good friend Kinsei posted this:
I also learned that you don't even have to bomb the base first before taking to your lunar rover! Here's what I did:
1) Pick up bomb
2) Drop bomb on rover
3) Drive to alien base
4) Bomb alien base
5) Pick up turret (just to the left of the alien base)
6) Drop turret on rover
7) Get back in rover, laugh all the way to the bank
That strategy cut down my vulnerability time of being OHKO-able by at least 70%. I spent about an hour and a half trying it before this strategy, and within 15 minutes of doing what I outlined above I was able to nail it.
I'll have to give it ago again. I've done the bomb the base and grab the turret but the 1 time I was able to pull it off I fell short on points.