There are many video graphics cards available, and the one you choose will largely depend on how you want to use it, what types of PC games or software you're interested in using, and how much you want to spend. Installing a new graphics card is not a difficult task as long as you select the right one to fit your existing system as well as your needs.
Upgrading your GPU may not provide the boost you were hoping for if you have a weak processor, a poor quality display, insufficient power supply, too little memory, too small a case or even poor cooling capacity. For that reason, look at the graphics requirements of the games you want to play, or the software you want to run, to see what is required or suggested, then use that as a baseline for selecting your new card. Also, be sure to measure to make sure the card you select will physically fit in the case.