i'm not sure if i'm too late, but if you haven't gone on your trip to nyc yet, here is my suggestion.

i've lived in nyc for 7 years and for the first 5 i had a car. i always parked on the street which is free. there are alternate side parking rules in most areas. this means that you have to move your car at certain times in order for the streets to be cleaned. however, these rules do not apply on weekends in some areas. if your arriving on a friday and you park, you may not have to move again until monday morning. also, in my neighborhood there is no cleaning on wednesdays so depending on when you arrive you can avoid having to move your car for several days and the street parking is free. just be sure to read the signs in the area very carefully or ask someone about them before you leave your vehicle.

again, i'm missing a few variables to your trip, but this could be an alternative to parking in a garage.

if you go the garage route...there are many garages all over the city. as others mentioned, stay away from times square and other touristy areas. i'd say that a typical cost for a reg. sedan is 25-35/day. an suv or large car is usually more. again, this depends on the area. i live on the upper east side and this is the normal price.

also, my friends and family visit often and almost always park on the street. it's no guarantee, but i feel it's reasonably safe and definitely cheaper!

good luck, and if you've already gone, maybe this will serve as advice for others :)