The CPU shouldn't be an issue at this point, just your graphics card (GPU). For that and the RAM, reseating would be to power down, disconnect anything (power) to the piece of hardware, and take it out. Next, put it back in again and make sure its properly and firmly in the right slot before connecting cables and trying to restart.
I didn't ask before how old the card was, but you can always try and contact the maker to see if you card was defective (if you recently got it). If you've had it for some time, or got it used, it's possible the card is on it's way out. I would try the above steps first before throwing your arms up in defeat and looking at a new card.