(you asked many posts back, and I believe you did not get an answer:)
if you plan on working with servos, you do not need a motor shield. a sensor shield might be something fun to have, to make prototyping easier.
you may want to check out robotoshop.com they have a bunch of "robot" arduinos, which have lots of little features which you will find usefull.
something like this: http://www.robotshop.com/productinfo.aspx?pc=RB-Dfr-36&lang=en-US (there are other similar products as well, you may just want to search around.)
I also found this: http://www.robotshop.com/productinfo.aspx?pc=RB-Dfr-152&lang=en-US (which I think could be spot on what you need)