Get 8GB of DDR3 RAM. 4GB is only enough for 720p computers with regular HDD's. They're slow and aging badly. I repeat, get 8GB's, you will thank me later.
You cannot change graphics cards on laptops, in fact you can't even change RAM on most, or remove the battery (need extra special torx screws). You can only change SSD or the HDD.
As long as you're talking Thinkpad. I made a conscious decision to buy a cheap Ideapad N581. It's cheap by any measure (i3, HDD, 4GB, ar8161, bcm4313, glossy crappy screen).
Plus apparently they thought they could save perhaps a fraction of a cent by using a crappy breaky screw for holding the hinge mechanism, meaning that 4 months after buying it (and having never used it outside home) one side of the hinge just broke and now I cannot tilt the screen without making the whole situation worse.