I think you'll find between the costs and the risks it will be cheaper selling your system and buying a new unit with the features you are looking for.
To start with changing out logic boards between system series can be risky as things are moved about. Sometimes its as simple as the logic board standoffs that mess you up. It appears Apple has continued the series across to the Mid-2014 by their Model ID.
The rule of thumb is swapping out within the series is doable in your case MacBookPro11,1 so you could swap out your i5 2.4GHz to a i5 2.6GHz or a i7 2.8GHz logic board which could be loaded with 8GB of RAM (vs 4GB) all within the series (Late '13).
As to the Mid '14 carry-over lineup I'm not sure here. Apple could have altered things physically but kept the logic the same. I doubt anyone has even thought this through or compared the logic boards to even see if its possible. Basically you're the pathfinder here. Let us know if you decide to give it a try what you discover.
Again, I do think this is a risky adventure and you will be happier with a new system.