PREREQUISITES: MM #20 (Friends Reunited), Must be Trevor.
1. Skin of your Teeth: Exit the car just before the train hits.
2. Kill Al Di Napoli using the train.
Turns out that kidnapping a movie star is harder than it sounds. Or, well... keeping said movie star is anyways. Since getting his favorite pizza is out of the question it is time to end this.
Get in the car and start to drive to the destination. On the way you'll talk to Al - there's some very good dialog here. Very good. Along the way you will get a choice though: continue on with the plan or let him go.
Continuing with the plan:
You *must* do this to get a gold medal on this mission. After all, the two medal conditions are dependant on killing him. Take him all the way to the destination using the highways and freeways. Once you are there you can either get out and watch from afar or go for the medal and exit the vehicle right before the train hits. Now, you get out of vehicles too slow to do this safely so what you have to do is to speed towards the train as it is coming and then jump out. That's pretty much the only way to get the "Skin of your Teeth" medal.
Letting Al Di Napoli go:
Keep driving and enjoying the conversation until he brings up the fact that he'll give you $10,000 dollars to let him go. Good news for you if you need the money: he isn't lying. You can pull over and go to the trunk and let him out and he'll give you $10,000. This is actually the smart first choice as you get the money and can always re-play the mission later for the gold medal.
No matter what you choose the mission will be over. If you killed him, Trevor will call Nigel and let him know of the unfortunate accident as well as wishing him a good vacation.