Every manufacturer is different, but I doubt if it's a slip fit with a gasket. Too great a chance of leaks/odor.
Better plan on cutting the pipe(s).
According to the plumbing diagram from Winnebago, MY rig has one pipe plumbed into the top of the grey tank, the vent pipe. The kitchen sink drain T's into that pipe, and the shower drain T's into the sink's drain pipe before it gets to the vent. (My bathroom sink is plumbed into the black tank.)
Yours may have 1 (plumbed like mine), 2 (vent and sink(s)/shower), 3 (vent, sink(s), shower), or even 4 (vent, kitchen sink, bathroom sink, shower).
Bobbo and Lin
2017 F-150 XLT 4x4 SuperCab w/Max Tow Package 3.5l EcoBoost V6
2017 Airstream Flying Cloud 23FB