Vent selector not working!

[superslick]

Hello chaps
Long time lurker here, in need of some advice. I've got a 1996 Xantia SX 1.9TD with Air-con, and the the vent selector doesn't work. I've checked the cables behind the heater controls and they are all connected. When I move the vent selector lever, I can hear slight movement. I think the whatever is at the end of the cable (behind the glove box? isn't working.
I'm thinking that the best course of action will be to take the dash board out, how easy is this for a basic home mechanic?
Any hints/advice would be appreciated!! [:D]