Unless it was lost in translation, that does not make a lot of sense. A 147 gearbox has 3 seals. 1 for each driveshaft, and 1 for the clutch shaft. It wouldn't have a '5th gear seal', or indeed any seal for a gear.
Chances are its a driveshaft seal, as the clutch seal is part of the clutch bearing assembly. If it is the clutch seal, it means removing the gearbox to fix. Drive shaft seals are easier to fix. Gear oil is about 10.00 a litre, a typical 'box takes about 2 litres.
The inner rods of the steering rack are unfortunatly not supplied as a seperate part, so a new or s/hand rack is the option.