You will not be able to install a dedicated graphic card. Only specific gaming laptop models will allow you to do so and they generally start at around $1,400 USD.
You will not be able to upgrade the CPU since it is soldered into the motherboard.
Most laptops will allow you to upgrade the RAM, but some do not. For example some ultrabooks have their RAM soldered into the motherboard and there is no RAM slot for you to install more RAM. Which specific Dell laptop do you have?