Removing drain pipe from grey water tank

[Bob N.]

I need to cure a small leak in the grey water drain piping on my 19RD. The drip appears on the blob of adhesive on the bottom of the fittings shown in the first photo. I have gotten the diagram of the drain lines from the factory but I am still uncertain of how the transition is made from the tank to the drain piping.

It appears there is a 3” inch ABS nipple clamped to the tank outlet. There are two hose clamps on the nipple that I assume are there to hold it onto a tank nozzle. It looks like a coupling is slid over that with some sort of soft adhesive or putty to seal it. A Valterra eccentric reducer is cemented into the end of this coupling.

My plan to attack this is to unbolt the grey water drain valve then attempt to pull the reducer/coupling straight out. Assuming I don’t find any cracks in fitting I would re-seal the joint with appropriate sealant and put it back together.

Can anyone who has have taken one of these joints apart let me know if this is a correct approach. Can anyone tell me what sealant to use?
I have attached some photos and the drawing from the factory for reference.

Thanks for any help you can provide.

[ALJO]

Just replace what you need. Sometimes you can chisel things out, but you have to be careful and know what you're doing. You have to use ABS glue for the black pipe.

[Grumpy]

What am I missing? Looks like a broken/cracked flange.