Best way to get to Concord area via Amtrak from NYC
I am going to the Concord area next weekend. Coming from NYC, and I would greatly prefer going by train rather than the shuttle. I need to be there early to mid-afternoon Saturday and back either late Saturday or earlyish Sunday. Is it best to take the train all the way to Boston or get off at the Rte 128 station? Also, is taxi reasonable from either to Concord or is it better to rent a car? If the latter are there any car rental places nearby to either stations? Alternately, how long of a drive is it from Nassau County? I have only gone to downtown Boston by train, never out to the Concord area. Thanks for any inputs.