No sir, you just have to get into the car to grab the weed, at which point it's on you and you just have to get to the drop off point in the time required/to escape the cops or whatever one it randomly is. At the end of the 10 missions you also get a special version of the Huntley Sport with a nice paint job, although you can still find them spawning in certain areas later on, although they're a bit rare. In fact, hailing taxis throughout that whole series of missions makes it so much easier, since you can just skip directly to your destination.
