Had a plumber come check on my leaky toilet. Turns out the Douglas valve is cracked and leaking. It's an older commode (Oct 2005).. it's a vitromex 6 LPF / 1.6 GPF. The plumber told me the Douglas valve is part of the tank and can't be replaced (so an entire commode replacement is needed. I haven't taken the tank apart yet to verify this, but eyeballing it I can't imagine they would have designed a ceramic commode with a plastic piece that can't be replaced. I'll add some images in a post below for reference.

I've done two of these recently, and it was a huge pain (relative to other toilets). You don't have to replace the whole commode, but you do have to pull the tank.

The flat head screws with a rubber gasket you have in the lower part of the picture will come out after you have the tank off, and then a large locknut on the bottom holds the valve/tube in place. My most difficult issue was getting the large lock nut off the bottomside and getting the swollen, hard gasket off of there.

I swore to my wife I'm never buying that style toilet again.

So are you a run of the mill handyman or a certified plumber? Ha, need to know how big of a pain in the ass this is to do myself. Because they want to charge me like $650 for a new toilet including installation.

If you are inclined to do it yourself, a new toilet only runs between $100 and $250 depending on model.

Need some extras like connection hose and an upgraded wax ring (my opinion)