Na mate. The gearbox is not opened, just split from the engine when changing clutch. Imagine the clutch as being sandwiched in between the engine and gearbox. For replacing clutch, the gearbox is just divorced from the engine and later mated with the engine again. If the oil seal to be changed is in the gearbox then three things will need to be done : 1. Split the gearbox from the engine. 2. Open up the gearbox. 3. Replace seal. Cheers. P.S. If you intend to keep the Linea for a long while, have the mechanic take a look at the gearbox bearings too and replace if necessary. Perfect time to do so.