Wuz I robbed? Inspiron 3847 not as advertised - ?

I just bought a refurbished 3847 (originally manufactured early 2013, service tag G246W12) from a third-party vendor via amazon. 

Setting it up, I found I couldn't set the screen resolution to more than 1024x768, despite the fact that the computer I'm replacing (a Gateway DX4840) immediately detects the appropriate screen resolution of my monitor (an XYGen MG19MY) as 1280x1024.

I looked at the Control Panel's Screen Resolution and Device Manager listings for both machines, and found that the display type, the display adapter, the adapter chip type are different.  I don't know much about hardware, but I'm assuming these differences are why I am having this problem trying to increase the Dell's screen resolution.

So I would appreciate any wisdom you can offer about two questions:

1. The "Wuz I robbed?" question is: The seller's listing specified "Graphics Coprocessor: Intel Integrated Graphics"; the actual machine's Device Manager says it has "Display Adapter: Standard VGA Graphics Adapter".  (The Gateway has "Display Adapter: Intel(R) HD Graphics", which sounds a lot more like what the seller's listing was promising.)  Would it be valid to claim that the adapter in the computer I received was not what the seller's listing promised?
2. Is an upgraded graphics adapter something that I could buy and install myself?  (My competence level is that I can do things like install cards in expansion slots and replace chips in chip sockets.)  If so, what would you suggest I buy?  (If this is not too hard, I figure it may be easier, cheaper, and faster than trying to get the seller to fix it.)

~ Thanks in advance

~ Ken

PS ~ I have posted screen shots of all this at https://www.dropbox.com/s/3lmv1v2945fcst4/DellScreenResolutionProblem.pdf?dl=0.