uh oh.. output shaft seal - big job

[StartX5]

Recently i posted a topic regarding the oil leak from the area of transmission drive extension and transfer case, i thought it's not the leak coming from output shaft seal but it is.
After long distance driving of >400 miles, i checked the leaking area again and this time, i found oil leak from transmission drive extension and transfer case. Hmm it's a big job! I have to replace output shaft seal and transfer case shaft seals too.

I am going to order output shaft seal kits from Cobra Transmission, did anyone order parts from this vender? Parts from Cobra Transmission quality are good? Are they OE direct?