1: With family not advisable. With friends 'YES YES'
3: Everything... Heating, oil leaks, timing belt age, fan belt(Highly tend to fail), power steering belt, All electrical, Wheel alignment regularly on trip, AC (to avoid windshield fogging), Power windows switches (Zeus, brand are not good make, so they fail very often), etc etc.
4: Yes it is, mine as well. Still facing even after brand new Safari radiator fitted.
5: All the things mentioned in point 3. As we are living with Sierra from so many years, a minute sound from anywhere of the vehicle will make you to start worrying until you trace and fix it.
LPG - Preferred to avoid.
Thanks