Your hard drive is SATA.
You can buy any size of SATA laptop ( 2.5" ) hard drive and install it in your model. E.g. 500gb.
If you would rather not lose the data already on the drive, or have to install Windows or your original brand name software installation from scratch , if you buy yourself an external 2.5" SATA hard drive enclosure (I recommend Vantec ones) and install the new hard drive in it, and connect that via USB to your laptop, you can use free software available on the web site of the hard drive manufacturer to copy the entire contents of your old drive to the new one, then swap drives. E.g. Seagate has MaxBlast .
Your video adapter is NOT a CARD - it's built into the motherboard, and it already has 3D capabilty.
Aspire 3680 support
Core Logic Chipset Mobile Intel® 940GML Express
It says in that - Mobile Intel 940GML/943GML Express Chipset (it says with integrated 3D graphics on the next page) for 3680.
There is no way you can have a better video adapter, unless you don't mind connecting an external monitor to your laptop, in which case you can get video adapters that plug in externally into your laptop.
Laptop video adapters, TV tuner examples
Service Guide (manual)
It's a bit older version, but the same probably applies - there is no video CARD slot.