To me there's something not quite right in knowing a problem exists, knowing a possible and cheap solution and then not doing anything about it. If you want to keep your car beyond the warranty period (I do - my car was an outright private purchase, not a lease) then preventative action would be wise. This reduction gear oil discussion was kicked off by an authorised Hyundai service tech who was replacing a reduction gear set that had failed at 40,000 miles (reply#119, page 6). The oil that came out of that gearbox was black syrup and his recommendation was regular oil changes to reduce the risk of similar reduction gear/bearing failure. At the rate we use our car we'd be well beyond the warranty period at 40,000 miles, so we, not Hyundai would be wearing the cost of repair. Plus there is the inconvenience of reportedly waiting for months while Hyundai sorts out warranty and parts supply. Regular oil changes are cheap insurance, IMO.
The magnetic plugs have already been found and are in regular supply. See
@KiwiME's post 144 on page 8. You may decide they are not needed - it has been determined that there IS a magnet in the gearbox (post #338, page 17), it's just not in a drain plug. Adding another one won't hurt, though.
Do yourself a favour, Lars, at least change the oil.