1: Integrated graphics are an advantage when they are capable of running the software that you have and you are on a tight budget, they are a good back up to have in the event that you have an add on video card failure and they are not power hungry like many add on video cards.
Personally I would say that having integrated graphics has no disadvantages, this because it is up to the end user to ensure that they have enough graphics power to handle any software or game that they intend using, for example, I would not recommend integrated graphics to anyone building a computer if they wanted a high end gaming rig capable of playing the latest games on high/ultra settings.
2: The 8150 is faster and the additional cores will be able to handle the more demanding software of the future, have it now when you are upgrading so as to avoid having to upgrade again further down the road.
3:Examples of OEM stickers that you will find
and full retail here
You are welcome btw