The cost of a clutch kit depends on the engine fitted 1.4, 1.6 petrol or 2.0 diesel (or 1.8 petrol if its a 4WD). see here for indicative £ prices - [broken link removed] + shipping.
No connection other than as a customer a couple of times.
It could most likely be the Gearbox. An expensive item.
Not likely to be the clutch if only trouble with a certain gear. If it were the clutch all gears would be a problem.