Milan is on the face of it one of the less remarkable Italian cities for tourists, although the best bits aren't in the centre - by all means visit the Duomo, but for eating / drinking and accommodation I would recommend staying in the Navilgi area - anywhere around Porta Genova should be good. Not sure about tickets for the San Siro but given the size of the stadium it shouldn't be a problem unless a Milan derby I would think, particularly given neither Milan side can be said to be at their peak at the moment. I was at a gig at the San Siro last year and was pleased to note they have extended the metro (red line from memory) right to the stadium.