I have a 2002 duramax that is leaking between the transmission and the transfer case . because of a bad gasket. Would this be hard to change my self? Or is it a job for the dealer.

Depends on how handy you are..It really isn't a difficult job, just a bit cumbersome..The gasket is cheap (less than 20 clams).
Make sure you inspect the transfer case well for any rub through areas...

Do a search for t case leaks, there is another more common reason they leak.
As foor removing it, how much can you bench press?

Do a search for t case leaks, there is another more common reason they leak.
As foor removing it, how much can you bench press?Is that with, or without, transfer case oil dripping on your face???

Is that with, or without, transfer case oil dripping on your face???
With, its pretty straight forward just kinda clumsy