You've basically got three airports to choose from. Linate and Malpensa are the two official Milan airports (even though Malpensa is 25 miles away!), and then there's Bergamo, used by most budget airlines. Check out flights at www.momondo.co.uk.
If you fly to Bergamo, the airport is actually Orio al Serio. It's about 30 miles north east of Milan. There are regular buses to the nearest station, from where you catch a train to Milan central station. Total journey time is about an hour and a half. It's an intermittent service, with some trains going to stations in Milan other than the main one. You can look up times here. A better option is the regular direct bus service between the airport and the main station. Linate airport is 12km east of Milan. The best way to get from the airport to the city is by bus. The No 73 service to the main station runs every 30 mins from 5.40am to 9.30pm; journey time 20 mins; buy your ticket on the bus. An alternative is to pre-book airport transfers with A-T-S.net who offer a shared minibus service, or a private taxi to take you to your final destination.
Places to stay
Last time we played in Milan most of us stayed at the Hotel Garda, which is a couple of hundred yards from the main station. It's a decent place, and worked out at reanoably cheap. Unfortunately the price can be twice that if there's a big conference on in Milan.
For other hotel options, try:
Club and ground
Known the world over as the San Siro, but officially called Stadio Guiseppe Meazza. It's quite a way out from the centre. You can get there on the underground. The recently constructed driverless M5 line, which runs every 3 or 4 minutes, reached the San Siro in 2015. Alternatively there's a number 16 tram from Piazza Cordusio, just west of the cathedral. Journey time is about half an hour. There are hardly any bars near the ground. In any case the chances are there'll be an alcohol ban in place on the day. Best bet for a drink is some quite locals' bar down a back street.
Official San Siro site
Official Inter site
Official AC site