The nearest station would normally be Oldham Werneth, which will be closed for the game as they're updating the tram system, so buy your ticket to Manchester Piccadilly and take a bus from the station.
The fares to get up there range from £22.50 to £98 SINGLE the nearer you get to kick-off time, the last train direct back to the smoke would be 21.15! So forget it, especially as there could be extra-time and penalties.
If you decide to stay overnight, , there are trains after 9.30 from £22.50 but you will need to win the lottery to get an earlier service to be back in the smoke to start work.
To check out what they've got at the moment go to: www.virgintrains.co.uk
Buses from Manchester Piccadilly
Services operate every 15 minutes or so on in the evening. Numbers 24, 181 & 182 make the 25 minute trip to Oldham and will take you to Boundary Park.
The 181 goes right past the Rifle Range pub, top recommendation in the S24 'Pub Crawl', and a short 10-minute walk to the ground.
The Oldham 'Loop' Bus Times: www.tfgm.com
Manchester Piccadilly: The blue blob, bottom right. Buses to Oldham: Piccadilly Gardens, top left.