Can I upgrade the video card in my 2009 iMac with the new ATI 2 GB VRAM card?

Question

I am looking for more video RAM for video, CGI and animation work in Blender.
I may purchase Final Cut Pro X in the near future and I need to make sure there is enough video RAM to be able to work with this version of FInal Cut.
I, currently, use Final Cut 4 Express and though this runs fine, through Rosetta, on my current setup, I fear this much newer version may need more graphics power than I have, now.
I, also noticed some lag when working with Blender.
No where near as much graphics or video/animation lag as when I using Blender on my old G4m but it's still slightly noticeable.
I realize I may have to install this myself.
Can I purchase, somewhere, Apple's 1 or 2 GB ATI card seperately or from a third party vendor and install, myself.
I have seen posts that tell that the 27 inch iMac has a removable video card and is not soldered to the logic board like in the 21 inch models.
If true, is there a complete procedure for the iMac breakdown, installation of the video card and reassembly procedure?
My iMac only has the stock 256 MB VRAM graphics card.
If the take down looks more difficult than I feel I can attempt, I have an Apple authorized reseller, repair facilty here, in my area.
Could I purchase the card and have them install it for a fee?
ThanX for all of the info and advice, in advance
Michel

Answer 1

You will need to check if your model originally was offered with a custom build option that included a different graphics card. If so, you may be able to have it done; here is a fellow who managed to do it on a 2011 iMac (graphics card not soldered) and the model originally offered a better card option:
https://discussions.apple.com/message/18919734#18919734
Is this yours:
http://everymac.com/systems/apple/imac/specs/imac-core-2-duo-3.06-27-inch-alumin um-late-2009-specs.html
In particular, click on the link in this section of the specs:
I'd check either with Apple and/or an AASP to see if it can be done with yours or if yours is one of those where it is part of the Logic Board/soldered to it.