Change a 2009 LogicBoard into a 2008 Version. Please help

Hallo,

My Name is Jonas and Iam from Germany. So please try do keep your answer in simple english ! :)

First of all i have to say, that Iam well known in assembling technical instruments. But i have no experience in following thing:

I got an iMac 20" LATE 2008 A1224 (with 2,4Ghz Core2Duo) for a very good price !

I find out, that its just able to build in only 6GB RAMS DDR2! I also think, that the Graphics Card isnt well for me.

But I wish to add 8GB in DDR3 with better graphics.

On the Internet, I found a LogicBoard from EARLY 2009 iMac 20" A1224 (2,66GHz Core2Duo) with Nvidia GeForce 9400 Graphics on it (Part-Nr. 820-2347-A).

It seems to be no problem to swap the 2009 Board into the 2008 iMac. Visually both boards look fine similar to each other. So can somebody help me with those 2 questions i have?

1. Is it possible to swap the 2009er board into the 2008er iMac or will it cause damage? May you explain your reason, you have? Give a tipp ?

2. What happens, if i choose to put 8GB into the 2008er Version? Will it cause damage or just 6GB get recognized ?

I would be very proud of an answer, so that i can work it !

Thanks, Jonas