Here's the trick behind ALL of it:

Preparation: Defend your harvester before anything else. Keep it alive with an Engineer. When it rolls back to base, buy that Buggy. Get another Engineer in it.

Transit: Your Engineer is probably going to beg for the gunner position. Don't give it to him. You'll see why in a few. Drive your Buggy on the road in front of the Airstrip's drop off area. Take it down the road and go into the Nod tiberium field. Drive the Buggy through the hole in the wall.

Execution: As you see that Weapons Factory looming in front of you, you have to choose one of three choices: Either hit the Weapons Factory, Tiberium Refinery, or hide behind the Refinery and get a bit of repairs, hitting the Power Plant. We'll say we're attacking the Tiberium Refinery. As you drive along the large building on your right, fire thirty rounds into the Weapons Factory. EVA will announce: "Warning: GDI Weapons Factory under attack." Drive straight to the Tiberium Refinery's back entrance. All the the Engineers should be looking at the Weapons Factory. Pile out of the Buggy and plant your TIMED C4 FIRST on the Master Control Terminal. After you plant the Timed C4, put the Remote C4 on the Master Control Terminal. Wait until the two C4 charges detonate. Blow the Remote C4. Building destroyed.

In the case of you being found: Blow the Remote C4 IMMEDIATELY. Do NOT wait for the Timed C4 to detonate. At the very least, you damage the structure, you get credits, and you get valuable points as well. 65\% of the time, the building will blow regardless of if anyone has found you or not.

If your Buggy is still intact afterwards, repair it and drive home.