We just spent 3+ weeks in Amsterdam in September. I would highly recommend Hotel Sebastian. We spent one 1 night there but it was the best bed we had had in months. The onwers are wonderful. Send them an email and introduce yourself and they will take great care. Please tell them I said hello as well.
As for transportation the easiest way to get around is on the tram. You can buy tickets on there and they go to most areas of the city. There are certainly taxis as well and I have never heard of any issues at all there. I agree completely that the train from the airport into Centraal Station is absolutely the best and easiest.
Finally, in case you are looking for something a bit fun I recommend checking out one of the oldest bars in Amsterdam - Wynand Fockink - landingspagina
. It is a lot of fun and a great place to try jenever. I attached a picture from when we shared a drink with our friends there.
Have a wonderful time in Amsterdam. It is a beautiful city.