Not sure if anyone done this before and I couldn't find anyone actually connect this controller with XBee. Does anyone know the proper way to connect XBee? D0 & D1 won't interfere with anything else?
First off, it must be stressed that your x-bee is a 3.3v device. It needs 3.3v for power and it is expecting its data lines (rx/tx) to also be at 3.3v. The wild thumper is a 5v device and supplies 5v as well as any serial data coming from it would also be at this 5v.
Yes, you need to regulate your 5v down to 3.3v for supply power. Start there.
Next, you need to connect the RX and TX lines. A poor-man would put a 10k resistor (in series) on both of these lines and call it good (in terms of the 5v/3.3v issue). Many people have wired many xbee's this way and it has worked. This is not the ideal situation though and there is always a "frying" risk. The best situation would be to use some kind of level-switcharoo device. There are chips out there that do this, as well as countless optoisolaters that can be used. Do a little searching as to how to interface a 3.3v device to a 5v Arduino --There are countless tutorials out there.
From there, you will need to configure your x-bees. Again, do some searching here. There are countless tutorials out there to help you configure your x-bees into different "modes", baudrates, etc. --I have found that it is quite handy to have a usb/ftdi x-bee board for not only configuring the x-bee but also as a way of getting data from the robot into the computer.
When all of that is done, simply figure out what data you want to send. Remote control, "mapping" data, "debuging" data etc. etc.
Write code. Done.
The 2 arduinos would talk to eachother the same way you are going to talk to your x-bee. Your magic search term here is "serial".
Thanks for all tips. I will do more research on these directions.