Going through the top, you should be ok with just popping the 4 bolts at the end of the headers. Even if you break those bolts, you can drill them out and replace them with ones (Inconel and all) from the dealer. If you have an auto, I would recommend removing the transmission cooler hard line so that you won't have to tip the motor to get it in or out.
Take care of any maintenance on the new motor that is easily accessible like the knock sensors, hard cooling lines on the side of the block and other things like that. Depending on the age of the motor, oilpan gasket may not be a bad idea (or at least inspect for leaks).