I'm not a professional car mechanic and I've done a couple of these. Usually takes a couple days to disconnect and document everything (take pictures, mark parts, wires and hoses, etc).
Then to actually remove the engine, its another day or two.
So for a novice (and I'm not a novice, been working on cars for over 10 years), plan on at least a week to get the engine out (IF YOU HAVE THE RIGHT TOOLS).
What I have found is that it take a couple of weekends and nights to get the engine out and then about the same to put it all together. The elapsed time can be from 3 months to 12 months cause you're pretty sick of it after a while.
I also learned that its not worthwhile to do this unless the car is in really good condition. If the condition of the car is okay, then forget about it, not worth the cost or time. And after you replace the motor, its really not worth a lot more than before. So unless you're really persevering and focused, I'd pass on this opportunity.
Most people are happier buying a reliable used car and just driving it.