There will not be "tons" of taxis, but there will be enough. The dispatcher will call for them when people come out of the terminal and it will take ~5-10 minutes for them to show up but there will be enough to get you and take you on your way. If you get outside and the line is miserable you can just call 7s or 6s and they'll send a car around, again about a 10-15 minute wait most likely.

Taxi is flat-rate of $45 plus tip and $4.15 toll if they take the midtown tunnel. My guess is that a car service is not much different than that.

And, yes, they will let you sit up front if you do not want to do three across in the back.