You will not be able to add a graphics card to that laptop. You need to pay more attention to the laptop details prior to buying it. Also, you should have asked your questions prior to actually buying the laptop. That way you would know what to expect.
I can confirm that you will be able to play Mass Effect 3 on your laptop. For the hell of it, I decided to play ME3 on insanity mode with my Lenovo IdeaPad Y470 using the Intel HD 3000 graphics core instead of the nVidia GT 550m. I was able to complete the entire game. Performance wasn't great compared to the GT 550m, but like I said, I was able to complete the game.
I also tested GTA IV with the Intel HD 3000. However, I was not able to play the game at all. GTA IV could only "see" 50MB of available RAM for the Intel HD 3000. I was able to load a saved game, but due to the limited RAM, the walls, floors, and ceilings were not loaded. The character, Niko, was simply standing in empty space.
There are Youtube videos of people playing GTA IV using the Intel HD 3000 graphics core (using very low settings), but I was not able to do so on my laptop.
As for the other games you mentioned, I never played them so I cannot say. The only other game I tested was Fallout 3 and that game is playable with a mix of medium and low settings @ 1366x768 resolution. However, Bethesda's games do not recognize the Intel HD 3000 graphics core so you need to install a file called "d3d9.dll". In order to play Fallout 3.
"d3d9.dll" was originally developed as part of the "Oldblivion" project for underpowered graphic cards that were not capable of playing Oblivion. It basically tricks the gaming into thinking it was one of the nVidia cards. It can be downloaded from the following link.
http://fallout3.nexusmods.com/mods/17209/?
Since I finally decided to play Skyrim I will see if the Intel HD 3000 is capable of playing that game with the "d3d9.dll" file over the weekend. If I have time...