Need help with a toilet valve repair

[Betty]

We recently had the toilet replaced by the owner of the home we rent. (tank was leaking)

Within a week, the new toilet has decided it will not stop running. After playing around with the little screw on top and the floater thing, I believe it's actually the pump part that's the problem. It runs and doesn't stop no matter how high you adjust the floater. Manually lifting it didn't help either. You can hear when it's supposed to shut off but it just keeps going.

Anyway - I bought a new pump thingy - some quiet model that doesn't even need a floater.

The problem is I can't get the old plastic one out. I've disconnected the water hose underneath (after shutting off the water) but I can't get the plastic coupler off. Is there some trick I'm missing out on? It's a fairly cramped space - but I'm down on knees and elbow getting under there. It's hard to get a grip on it and since it's plastic, it's now got some edges worn down from trying to get it off.

Help me please oh plumbing-knowing-peoples!


*I thought it would be easy to fix ourselves. It takes the owner an hour to get here - we have to wait around half a day - and you know, clean the house and stuff. It just seemed easier to to it ourselves.