Mercedes sprinter sprinshift transmission?

My 2005 311cdi sprinter wont select any gear it just stays in Neutral. The transmission I think is called a sprintshift which is a manual gearbox that changes automatically by selecting gear up and down only and has a Auto option as well. I hope someone can help.
I have a 2005 Mercedes gearbox semi (I think is called sprintshift) would like to change to manual. Do I need a ecu, is it straight forward to convert it into manual
Thanks

ahmed, December 2012