RAM: each of the two slots can support up to 4GB RAM. 2 x 4 = 8, so yes, the board supports 8GB RAM in total.
Graphics card - the amount of memory on the card is irrelevant as far as compatibility is concerned.
What matters is the type of interface the card has, it must match the type of slot on the motherboard.
The board has four expansion slots as follows:
1 x PCI Express x16 slot
1 x PCI Express x1 slot
2 x PCI slots
You could easily have found all the above details yourself on the product page, under the "Specification" tab.
Most new graphics cards today require a PCI Express x16 slot so you are okay choosing one of those, assuming the slot is not already occupied.