I think you may have forgot a word in that, which I would assume would be "replace". I didn't have any problem doing a head/cam swap on Ben'* car (big_news_1) with a little help here and there in one week. If you replace the whole engine you have to unbolt the trans, unbolt the TC ---> flexplate, and unhook all sorts of things like you would with a head swap. I've never done that one though.
I'd just say that if you wanted, heads up with engine in car isn't too hard. Gotta stand in the engine bay sometimes on the trans case. No big deal if your skinny like me.