OK, it is easy, but tough i missed what's inside, i will tell you how to reach the Mendez Mansion's Safe easily :
1. Go to the Boxville out of the Mansion to control Domestobot.
2. Control him around like a car (that means it have the same controls of the car).
3. When you have a job from Armando, you must do it in time, or its failed, and you will have to start over.
4. When finished a job go to the kitchen, then into a gym-like room, enter a door which leads to the basement.
5. Use the signal and get near a door that looks like a refrigerator door, and this should be the SAFE !!!
5. The code of the safe is 8423, then when opened, use the lighter to crack it.
MISSION PASSED, you've also got the Boxville you need to deliver to the IMPOUND
I hope it helps you, and Happy Gaming ;o) !!!