Here is some information on people looking to go to the game(driving) and not staying in New York.

Merto-North Line runs along the Hudson River to the North of New City City... The train runs a few blocks south of Yankee Stadium.

Here is information about one of the stops to the North...(provided this one because the rest of the ones to the North stop and transfer to different train at this stop) Station has over 1000 parking spaces (but a Friday during the week could be alittle full)

MNR Stations
http://as0.mta.info/mnr/fares/get_fares.cfm

Looks like the train ride into the city would be about a 60min to 70 min train ride...
There is a parking price which is parking meters... can put 24hrs on one parking meter... Trains seem to run almost all day

The cost of the train ride itself is about $9 round trip... At the most the train comes about every hour(more trains during peak periods but peak periods do cost a bit more)

In the area of this there is a few towns within 20 mins with a few hotels for 110-150 dollars... Plus the area where the train runs is near West Point... May be a few more hotels in that area for people to stay...