Yes, there is a specific procedure. You need to start from cold so it'll have to stay there overnight for them to check the following morning. The temperatute has to be checked with VCDS. You also need a special filling tool as you have to pump the oil in from underneath. I use this:
With the engine running, watch the gear oil temperature in VCDS until it's at 30-35*C, then remove the large filling plug in the sump (17mm hex, not the small 6mm drain plug). Pump in oil until it overflows and wait for it to stop dripping, then put the plug back in. The oil temp mustn't go above 40* while filling. It'll cool down slightly as you add fresh oil.
Tbh if it was rebuilt only 25K ago and there are no visible leaks I'd be inclined to leave it alone for now and just check the F125.