There is a little more info on this brand here, but a quick look in the usual places says spare parts will be very hard to get unless you can get a scrap movement, so ask lots of question and try not to break anything
http://forums.watchuseek.com/f11/1960s-belforte-destro-custom-604277.html
First you will need to remove the small plate (cock) on the back that supports the centre secods pinion. The large wheel that drives this is a press fit onto the shaft which drives it. (If you look closely you should see the small steel driving pin in the middle of the hub of this wheel). Make a careful note or take a photo of how the bronze spring plate fits against the centre seconds pinion. This is a friction spring which compensates for the backlash between the driving wheel and pinion to make sure the seconds hand doesn’t move backwards.
To remove the large wheel then ideally you need one of these https://www.hswalsh.com/product/bergeon-30638-3-watch-wheel-removing-tool-hh53 however, you can also do this with a knife blade either side and levering up equally so as not to bend the shaft. The knife blades should be under the hub, not the rim of the wheel so you don’t bend the wheel. Just to make it more fun, the wheel can fly off suddenly if you use this method, so do it inside a plastic bag or cover with cling film first.
From this point you can disassemble as normal.