Engine replacement?

I have a 08 speed 3 i bought not too long ago it had been rebuilt from last owner. unfortunately whoever built the engine torqued a bolt inside too tight and the bolt head came off and went into a cylinder. from asking around I could not find anyone to properly rebuild it so I am looking to find a replacement engine and i see engines coming up saying for ms3 and cx7. I know the cx7 shares same engine but is it a direct bolt on? I know I probably have to use my own wiring harness and something about the turbos are different but other then that am I good to just buy one possibly being a cx7 engine and have it go straight in with no modding

 

Cx7 is the same basic architecture but is a different motor lower compression etc

 

So how would I tell which one I'm getting because I see all advertised as mazda speed 3,6 cx7. Also would the gen 2 engine be direct fit in gen 1?