Try the DIY route - it worked for us in April 2015 and this is how it went:
1) Buy a ticket on a minibus leaving from the main bus station in Krakow (located next to the railway station). There are quite a few of these minibuses and you will need to get an early one that arrives in Oświęcim (Auschwitz) around 09:30.
2) The reason for getting to Oświęcim early is that entry to Auschwitz I is by guided tour only from 10:00 onwards. Before 10:00 you can enter with a free ticket (that you need to download and print in advance) and then wander around by yourself. There are also fewer visitors in the early morning. Note that you cannot take in a backpack, or similar bag, that is larger than 30x20x10cm. Free storage lockers are available if you need to park a bag.
3) When you have finished at Auschwitz I you can take a free shuttle bus to Auschwitz II (Birkenau). Allow plenty of time here as the site covers a very large area. Entry is free and there is no obligation to take a guided tour. As you will be going in February, you will need to wrap up very well especially if it is windy. There is no shelter from the weather at Birkenau other than inside one of the unheated barrack huts where the prisoners were kept.
4) When it's time to go back to Krakow, you have a couple of choices: a) find a minubus going back to Krakow or b) take the train. Oświęcim railway station is about a 1km walk from Birkenau. There are direct trains to Krakow but they are fairly slow, although that does give you a chance to see something of the countryside.
Language: we found that bus, railway and Auschwitz staff spoke English so no problems with buying tickets etc.
Check this website for more details:
http://auschwitz.org/en/visiting/hth
Neddy