Got all the parts... any tips before I start?

Hey all, so I have a simple idea for a robot, hack a hexbug spider and put a Sharp IR sensor on it to make it autonomous.

 

I have:

1 hexbug spider

1 Arduino UNO

1 Seeed Studio motor shield

1 Sharo IR sensor from the SH robot

all the hook ups, solder etc.

 

Heres my question; would it make more sense to hack the existing chip on the spider, or cut it out and just have everything go straight into the Arduino? 

 

If you have any tips or such before I get started, that would be really appreciated!

and if you see any similar projects, please let me know!

heres a link…

http://www.amazon.com/Innovation-First-Labs-Hexbug-Spider/dp/B004OLIJFO/ref=sr_sp-btf_title_1_12?ie=UTF8&qid=1385672839&sr=8-12&keywords=hexbug+spider

 

The uno sits on it well, but the battery pack makes it just a bit overweight for the motors.