It is indeed a massive and beautiful structure , the painting and sculptures inside the Duomo are worth seeing. We had not seen such a beautiful cathedral in the past, but then we haven't seen many. (Tram 1, 2, 14 will take you to the Duomo)
For the ladies, if you wish to go inside the Duomo, you have to cover up your shoulders and not have too much of your legs showing, otherwise you won't be able to go in.
I would definitely recommend visitors to climb to the top of the Duomo...or you can take the lift..It cost 5 Euros to climb or 8 Euros to take the lift, which you can buy on the door. You can stay up there as long as you like and its a great place to sit and chill out, while getting a tan
The best part of this visit was climbing the stairs to the roof. There are I think 150 steps up or you can get the lift for a slightly higher charge. The first roof is an amazing view, another 30-40 steps up you can go to the next level which is just spectacular.
It is obviously quite a climb but worth all the effort, coming down can make you a little dizzy but this attraction is a must if you are in Milan.