Sounds like a problem with the clutch,gearboxes don't usually go wrong unless they are seriously abused,have the clutch checked,if you can select the gears ok with the engine turned off it is a likely cause.
Rich
March 2008
I can answer this question...
I FIND IT HARD TO GET GEARS ITS GETTING VEREY TIGHT TO SELECT THEM?
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.