Where to stay? This is like my biggest nightmare cuz I dont know where to stay!!
I just need some bed space!
You can stay in a hotel or can get a bed space. Obviously hotel would be an expensive choice and you won't find bed space online like hotels. You can however check Dubizzle.com for bed spaces. You can't decide which one is better unless you visit it personally. Therefore, you need to have some support for at least a week or so during which you can find a reasonable bed space.
Once you get one, your life won't be the same. As you have mentioned you are a pampered child; be ready to face some harsh world then.
Which visa should I apply for? Can it be extended? If yes, then how??
Apply for 1 month visa that can be extended for another month. Prices vary. We sell 2 Months visa for AED 1500/- after all the guarantees etc.
Where to look for job? Any particular idea where I should go to drop off CV's or any other place to look?
Try getting in touch with recruiting agents before going to the UAE. They can suggest you where to apply and drop your CVs after having a look at your expertise and experience.
What to expect from a job? I've done MBA in Marketing, how much should I expect?
As an MBA in Marketing and if you have good enough experience (Minimum 5 years Solid Experience), you should expect a reasonable salary. If you get a job in a Private small company, they may not offer you good. Bug companies have better packages. 5000 Dhs is not a good salary at all. Neither is 7000 Dhs. If you have no issues in what standard of life you spend, then you can live a basic life in 7000 Dhs. You may not own a car, or live in a good house, or do regular shopping or do some aeyashi but you would be fulfilling basic needs and saving something as well. That something will have value in Pakistan but not in Dubai. If you plan to marry and move your family there as well, 12,000 Dhs is the minimum you want for an average life provided your kids are small and are not going to school.
Keep in mind some small companies charge you for the visa costs as well when they give you a job.
What will be expenses? Take me as a very pampered guy who always lived with his family? So now I have no idea what my expenses will be!! 
Just let me give you a basic breakdown for an idea. (single person spending time and not living a life)
Bed Space: AED 1500-2000 per month in a reasonable place in Dubai.
Khana Peena: AED 1000 per month
Moving Around: AED 500-700 per month
Baqi left right ka kharcha: AED 1000 - 1500 per month
Adding the minimum: AED 4000 Per month. If you get 5000, you can send 1000 i.e. PKR 27000 to Pakistan. I hope you can understand a life in AED 4000/-
Some other details that I am missing....
There are many things related to living in the UAE. That one gets to know when he goes there.
P.S: If u are here just to comment k apna mulk apna hota hai, time waste karo jakar, Arab mai koi izzat nai Pakistanio ki, bla bla. so please a humble request, apna aur mera time mat waste krain, shukria!
I don't have to say you left right ki baatain to waste your time. But if you go there for 4000-5000, you would be eventually wasting your time unless you are not focused in getting something better.