Thanks a lot Brad for the very useful info. I had the same early 2011 logic board that suffered from the well known GPU problem. Based on your postings I decided to replace it with a mid 2012 2.6 GHz logic board. The whole operation took me about 2 hours. The most difficult part for me was to connect the LVDS cable, the connector on the mid 2012 board seems a bit smaller.
The board that I received was just the board with all the chips on it but no provisions for cooling of the chips. It was quite easy to transfer the heat pipe of the old board, but nothing was foreseen to cool the Thunderbolt controller and the Intel BD82HM65 Platform Controller Hub (I looked that one up ;-), also no screw holes present. I took both the covers from the old board and 'glued' them on the cooling past on both controller chips. Of course this is a very imperfect temporary solution which is holding now for a week. I'm not sure what the final solution looks like for this. The screw holes mounted on the old board can only be taken off by using a lot of violence - I'm not sure if I will succeed without ruining them. But further I see no room on the mid 2012 board to put the screw holes as there are electronic components scattered around at the spots where the screw holes should be positioned. Even with non-conductive superglue I doubt it is a good idea to fit them on the new board. So I am very curious Brad how you managed to do that!
Either way I am very happy with my 'new' MBP.