Your laptop (equivalent to Toshiba A355 Satellite) can have a maximum memory of 2x4GB DDR2 (DDR2-800), a total of 8 GB only.
Most of the Satellite series have an empty 2nd HDD bay, but there will be no connecter to connect a HDD. So you may place a 2nd HDD in the spare bay, but there is no way you can connect it to the system. I suggest you open the spare bay cover and check for the connector inside.
In a laptop the graphics are integrated on the motherboard and it is not possible to replace the graphics adapter with another one.
But Toshiba gives you various models with different graphics options. Some have Intel, NVidia etc. You have to choose the model before you buy the laptop.