After completing the Find the Buggy Parts job, talk to Dan to start this one. You'll get a sniper rifle and explosive charges once you start the job. Be very careful while you're going around the corner sniping because the enemies are pretty accurate at distance with their rockets. There is also a nice cement tube to snipe from to the left around the corner.
Once you snipe all the enemies, plant the explosive and get back. Then tell Dan that the job is done. On your way back you'll get radioed the Durar's Time Trial job. You can also talk to Dan again for Dan's Message job.