The Stratford Metro North Station is located off I-95 at exit 32. From the station it is 59 miles to the Grand Central Terminal in New York, and the trip can take between an hour and fifteen minutes and an hour and a half, depending on if the train is an express train or not. The fare to Grand Central is $12.50 one way, off peak. It is more during peak hours, and cheaper web fares are available. Ticket machines are on the platform.
If you don't have a parking permit, it is $5 per day to park, and there are limited non permit day parking spaces. On the north side of the tracks there are only about 14 day parking spots, and on the south side there are more, but if they are full they suggest going to another station, the closest on each side are Bridgeport and Milford. Other large nearby stations are New Haven, Fairfield and Stamford. To see all stations see the map here
Overnight parking is at your own risk, and since you can only pay one day at a time, you will get a ticket if you park overnight, however it is only for the parking fee of $5, so the only difference is that you have to mail in the payment.
For more station information visit this page.