Ok well first thing I would say is, make sure you don't try and power the motors from your Pi! Motors tend to be very current intensive which will burn out your Pi's GPIO ports. So make sure you get an external power source for your motors.
As for controlling your motors.
If you can get away with simple on/off with your motors, and only want to drive forward. You could use the PiBorg PicoBorg - http://www.modmypi.com/raspberry-pi/bre ... ontroller/
If you want more control over your motors (forward and backwards) you'll probably want to upgrade to the PiBorg PicoBorg Reverse - http://www.modmypi.com/raspberry-pi/bre ... ontroller/
As for your servo, any of the following should do, each of them have their own benefits, so make sure to read the description to check which one will suit your needs the best
Servo Controllers:http://www.modmypi.com/raspberry-pi/bre ... e-support/
- Support for 4x servos - Support for 4x Ultra Sonic Range Sensorshttp://www.modmypi.com/raspberry-pi/bre ... t-pca9685/
- Support for 16x servos - Stack multiple boards to support up to 992 servos!http://www.modmypi.com/raspberry-pi/bre ... servo-hat/
- Support for 16x servos - Stack multiple boards to support up to 992 servos! - HAT format
Please note, if you decide to use the Servo HAT, and the PiBorg PicoBorg, you'll need to use an extended header so you can plug the PicoBorg on top of the HAT:http://www.modmypi.com/raspberry-pi/gpi ... xtra-tall/