The CPU will bottleneck most GPUs you put in it. What games do you play? (if you plan on playing games, more like, what do you plan on doing) Also, you will need a new PSU. As for the RAM, if you have it, you know what it looks like. There should be two clips, one on each end on of the slot the RAM fits into. Undo those clips by just pulling them back, align the RAM, and push it into place. That's basically what you would do with the GPU too. Just, there is only one clip. After you install the GPU, screw it in the back. After that's all done and it is in the machine, install the GPU drivers off the website. After that, disable to iGP in the BIOS and call it a day.
Hope this helped!