I have a 1981 240D w/ a siezed 4cyl normally aspirated engine. I found a guy selling a 5cyl normally aspirated engine out of a 300D. He said the engine would fit in my 240D. Is this accurate?

Addiitionally, their is anothr guy selling a turbo off of a 5cyl. If, in fact, the 5cyl will fit in the 240, how hard will it be to retro fit the turbo to it?

I appologize in advance if these questions seem rediculous, I'm new and just beginning to learn.

Thanks