hi fiat guru here,
Yeah if you look at the bottom half f your gearbox there will be a filler plug (size 12m alan key) put gearbox oil in there and if your checking the level, put your finger in and see if you can feel it or if its slowly dripping out , the level is ok
When you're checking the oil level, make sure that the car has been stopped for a wee while otherwise you'll get a false level because some of the oil will still be around the gears. By rights you should add oil until it starts to trickle out. This is because oil will gather at the level/filler plug and you'll think it's fine when it's not.
It should only take about 15 minutes or so to change the oil. Just make sure that the car is on the level when you're refilling it so you get a true indication of the oil level.