8 3/4 dif

I'm in the process of changing all the fluids in my newly acquired 70 Swinger 340. Is the preferred method for the differential to suction the fluid out or to break the seal between center section and housing. If there is a drain plug somewhere I need new glasses.
Thanks, Jerry
Since it's a "newly acquired" car, I'd pull the cover and have a look around inside just to make sure that nothing is obviously wrong.