Hi the sealed bit is a load of garbage, they only ever did a sealed gearbox 2009-2011 with catastrophic results, Ford did a sealed box on the early MK4 Mondeo it was designated power shift and was a huge failure, when I asked the dealer when I first got my car at 38k the exact term was gearbox is FILLED FOR LIFE, then emailed Audi in Germany who said, No change the oil every 50k or five years, if you think about it all that high grade sintered steel flying about in a bath of oil with the occasional bit flying off which is suspended in the oil until it by force of gravity hits the bottom of the casing, now imagine the same scenario with burnt worn oil, believe me it wont end well, I change my oil every year and as you said add SLIK50 you can't go wrong with that and a couple of bottles of Fuchs Titan, new box [manual] is just over five grand +fitting, DONT GO THERE.
Steve.