Although the motor shield you referenced is not ideal, it will probably work.
It sounds like you have read about the analog input on our jrk motor controller. The descriptions and documentation on that controller will probably not be useful for your motor controller. You should be able to control the linear actuator like a brushed DC motor.
Should you decide to use out jrk motor controller, please be aware you will need to write your own code to control it with an Arduino.