You can read my (extensive) blog post on the subject if you wish! That will give you a lot about the race itself.
Even if you don’t own a bike box, there are generally many places to hire them from. Personally, I would do that. The bike shipping options are seriously expensive for what they are. You could even drive! I flew Thursday night, and the airport is only a 15min train from the central station. So easy.
As for where to stay, I’d stay centrally, between the central train station and the race site. I stayed right by the central train station and it was a 10min walk to registration etc. It’s split transition, but that was not a problem at all. Public transport runs 24/7, and there are fast trains/metros to the swim start area for Saturday racking/race morning, and you can take your bike on the trains (you normally have to pay extra, but for Ironman weekend they waive that). Staying close to the finish, where you pick up your bike and bags after the event is so much easier, than having to wearily transport all your stuff back towards the swim start area after the race.