I can't answer everything because Ive never done an engine swap... on anything... lol, but I know it is possible, and you will get more power if you swap, but yes it is not a huge amount. the reasons I see to swap is that yes you will get more power, aftermarket accessories are easier to find, and Bill can write the tuning needed for a swap, plus customize everything else about it. The negatives are yes, it will be complicated no matter what you do, it costs money, but idk if it is more than doing a 4.6, and it will take time and troubleshooting to make sure it works right.
for what you are using it for, I would bet that you would welcome the extra power that it gives you.
to answer your last question, the least complicated would be to buy a new truck, then replacing broken parts on your engine, then to replace it with a matching 4.6, then replacing it with a 5.4.
hope that clears up the mud a little bit
