Chevrolet Tahoe Crankshaft Rear Crankshaft Seal

I Have A Leaking Rear Main Seal Which I Thought It Might Be, So I Went To Take5 Oil And They Confirmed. It' Not A Bad Leak At This Point...

My Vehicle Starts To Vibrate Around 60 - 70 Mph. It Feels Like It Coming From The Rear. Mainly On The Passenger Side.

I Dropped My Transmission Recently To Do A Rear Main Seal And I Put Everything Back Together (i Torqued Down The Fly Wheel And Everything)...

There Is A Leak From The Back End Of My Vehicle. My Father-in-law Says It May Be The Rear Seal. How Can I Confirm This And How Do I Fix It...