Confused with Xbee and Arduino

I am working on a project for a team at school that involves communicating with a computer to a car. On the car is an Arduino mega 2560 and multiple sensors. Although I am rather new at this, I understand how to use the few sensors we plan on and have done simple sketches on the Arduino. I also would like to design and fab a shield, more for learning than practical purposes.

1) I am confused because i do not know whether the xbee shields that exist are Arduino mega compatible.

2) Also, if I was to design my own shield, what pins would xbee connect with the arduino? I know the mega has separate communications pins that the UNO does not, whould I use those? Also, what circuitry is required, I know a 3.3v power and were to put it, but everything else I am confused about.

3)And third, I am very new to eagle cad and have used Fritzing before but it has its limitations. How do I get the correct spacing for the pins and other components?

Here is a Tinycad generalization of what I want, correct me if I am wrong with the schematic .

http://dl.dropbox.com/u/21442974/EVT%20electrics.png

Thanks, Tom

what pins would xbee connect with the arduino

XBees talk to Arduino through serial (Tx/Rx). If you use SoftwareSerial library, any pins can be used for serial communication.

1) I am confused because i do not know whether the xbee shields that exist are Arduino mega compatible.

Depends on the shield. Most are.

2) Also, if I was to design my own shield, what pins would xbee connect with the arduino? I know the mega has separate communications pins that the UNO does not, whould I use those? Also, what circuitry is required, I know a 3.3v power and were to put it, but everything else I am confused about.

Then, you are hardly ready to be designing your own shield, are you?

3)And third, I am very new to eagle cad and have used Fritzing before but it has its limitations. How do I get the correct spacing for the pins and other components?

Start with an existing shield design, and delete what you don't want.

Thanks for the replies. I am confused with what you mean by changing an existing shield. Do you mean I should edit it in eagle or do you mean I should by a proto-shield and build off that?

I should by a proto-shield and build off that

XBee has 2mm headers instead of the usual 2.54mm (0.1") spacing on the protoshield. You cannot (easily) fit the female headers for the XBee on the protoshield.

I have decided on buying the expansion shield by DF robotics. It has headers for sensors and xbee spot. Also, I knew the spacing on the xbee was different but the person who originaly gave me the xbees also gave me the spakfun breakout boards for them

Thanks, Tom