No, search as in the button on top of the screen, also www.sentra.net and www.se-r.net and www.nissanperformancemag.com. This topic has been beat into the ground time and time again. But just so you won't waste any more bandwidth, yes you need the harness and no you won't be able to do it in a day.
You need wiring harness, and ecu, and I'm pretty sure you can't do it in one day. It took a Nissan mechanic over a week to do my swap, and that was just putting in another SR20. You will need a lot of extra parts, and just when you think you have everything...you dont.
I havent done it yet, but if I ever do I am gonna just get a whole front clip from the dash up. Then its just a matter of ripping mine apart and replacing as is in the clip. Little more cost, but then you know to be sure.
I strongly suggest using the sr20 engine harness. Because if you don't, you will have tons of problems like me. Feel free to hit me up if you want to see all the problems associated with not using the harness with my DET. It could be conisidered a "scared straight" tactic.