they are really easy to service.
leaking from the U-turn leg is very common.
You basically have some oil in the air spring cartridge and some oil in the lower legs for bushing/stanchion lubrication. You also have this lower leg oil in the damper leg and then a large quantity of oil in the damper itself.
I think it’s 15wt in the lower leg and air spring and 5wt in the damper from memory.
The oil is just coming out of the lower leg of the U-turn side – not the air spring as all your air would be gone long before the oil. All you need to do is top it up – I would drain out as much as you can and then top up with the correct amount or just drop off the lowers completely and wash the old oil out with IPA and top up both sides. That way you know that you have the correct amount in both sides as they can often be a bit low from new.