It’s doable! The cases are the same. I’ve done a few with great success!
There is one issue you’ll need to deal with! Apple altered their LVDS cable connector supplier, the logic board connector is a bit smaller so you’ll also need to either replace the displays LVDS cable or if you have the skills carefully file with a fine emery board file the edge of the cables connector (both sides equally).
You only need a few strokes per side!
Here's the IFIXIT guide to replace the 2011 logic board: MacBook Pro 15" Unibody Early 2011 Logic Board Replacement as you can see its exactly the same for the 2012 mode here: MacBook Pro 15" Unibody Mid 2012. The steps are well laid out as long as you take your time and not force things you should be OK.
As to the logic board IFIIT sells them. Presently they only have this one: MacBook Pro 15" Unibody (Mid 2012) 2.3 GHz Logic Board which is this Apple part number 661-6491. The 2.6 GHz Logic Board is this P/N 661-6492 and the 2.7 GHz Logic Board is this P/N 661-6493. If you wanted one of the latter two send IFIXIT an email to put you down on there waiting list so when they get one in they can notify you. These boards are getting harder to source so you will need to wait awhile.
We don't use board numbers as that does not fully identify what the board was populated with CPU & GPU wise. It's only useful to ID what set of schematics & board views one would need if they where trying to fix the logic board.
I have no problem filing the cable as I outlined. If you feel this is hard you’ll need to carefully pull the display assembly off so you can reach in to release the latch on the display and carefully ease out the cable to replace with the newer one (which is the correct size). Lastly, I don’t offer systems already converted to sell.
If you live in metro Boston in the states then I could offer my services to fix your system. I presently don’t do mail-in’s and I’m not setup to do anything internationally.