Thank you once again, everyone. You've saved me a lot of time,
trouble, worry, and money! I looked up the map of Narita online, as
suggested above, and I think I know where to find the JR counter. I
might just pick up a shinkansen ticket as soon as we get into Tokyo.
Or, I can wait until we get into Tokyo and get to one of the stations
as also mentioned above and purchase the ticket then. That makes an
awful lot of sense! I guess there's really no need for me to depend on
the agency to make those reservations, huh? And I should be able to
get 2 tickets easily, right, as long as I don't wait until the day of
travel?

And just to confirm... the JR pass works for both the shinkansen
(except the nozomi), and the JR metro trains in Tokyo, yes? thank you
for the tip!!

Also... where is the "Station" from which the shinkansen depart in
Tokyo? I was a little confused with that. Do hotels usually have
shuttles that go back and forth to the stations? Is it possible to
take the bus? I am worried about how expensive it will be in Tokyo to
take a cab, when we get back there from the Shinkansen!

I read that carrying suitcases on the shinkansen is a huge pain... what
do people usually do? I realize I am going to be in big trouble, as I
already know I am going to by a lot of goodies, and I'm the first to
admit that I'm no weight-lifter!

Thanks again, everyone for being so patient with all my questions, and
for being so kind and sharing all your knowledge! You are really
wonderful!!