Help Hardware: CDMA to GSM

[jnthnbgg]

I was aimlessly wondering around the internet looking for a replacement camera for my i9020 and I noticed they have a sim card slot/board out there a well. My question is this being that this a CDMA phone and the radio is separate from the mainboard (reffer to link 2 at bottom to better understand what I am talking about) can I purchase the GSM sim card baord and slap it on there and go to a company like strait talk? Or is there more to this CDMA and GSM that the mainboard has built into it as well?
Thank you for any help on this issue and please keep the comments to this topic and not purchasing a new phone and the likes. Thanks again.

LINKS:
1) replacement Sim Slot/board: Samsung Nexus S i9020 SIM Tray Holder with Flex Cable Connection - Parts4repair.Com

2)Installing Nexus S SIM Card Board Replacement - Page 2 - iFixit )

 

[jnthnbgg]

Anybody have any idea on this topic? To make it a bit more clear if there is some question of what I am talking about. Can you take the radio from the Samsung Nexus S i9020 (GMS) and put it on the Samsung Nexus S D720 (CDMA) the radio connector is the same. Does the mainboard work universally or is it tied to one or the other? Thanks