Display issue (with flicker) after installing SSDI managed to replace HDD with SSD and everything was fine. 3 days later, after I installed Adobe Master Collection and reboot...
Answer to: Can I upgrade early 2009 iMac Graphics cardTechnically you can replace the Graphics unit with another, but the compatibility is not tested for larger-memory card. However, keep in mind that you will have to use the same board as in your current iMac, which makes the mission very very hard. If you find your system slow, think about replacing the HDD with SSD. This will increase App launch speed significantly.