2006 F150 Pinion Seal

So i have a F150 I bought new, has about 50k miles on it and i noticed some dripping by the rear axle. I have come to find out its the rear pinion seal most likely. I have read around and found its a pretty common problem. Has anyone had this problem and know if its covered under warranty??

I dont tow ever with this truck, never really put much in the bed other than a motorcycle here and there. Should this seal be worn out already. I can only imagine if i was towing a trailer everyday what it would be like.

Also anyone know what ford charges to fix this if its not covered under warranty? My local mechanic said about $250.00 if its just the seal. If the bearings bad as well it could be costly he said $750-$1000 range.

Thanks
Rob