If the donor car is complete, a good mechanically inclined person could do the swap in a weekend. I personally would give myself 2 weekends to do it. I would pull the engine with wiring harness attached, transmission and rear from the donor car in one day, and spend that evening cleaning up the donor engine, trans and rear and K member, making sure it's good to go for the swap.
The 2nd day, I would pull the engine and transmission along with the wiring harness from the good car. Again, pulling the entire K member will save you a ton of time. Get it all out of the way, and bolt the new engine, transmission, and K member in place. This should be easily accomplished in a weekend, as long as you've got a decent place to work, and good tools.
Then it's all about hooking the wiring up, and if you kept the original wiring harness in tact, it should be very easy. By the end of the 3rd working day, you should be ready to fire it up, but of course, problems always arise. Then you should have a full day to swap the rear ends out, and be on your way. That would be my 2 weekend plan, as long as I had a shop or nice garage to work in with good tools. Air tools are especially helpful in this situation.