Can anyone give some advice before we replace a worn-out toilet with a new one?
Advice on what?
Call a plumber.
Do you want a one or two seater?
**** flows down hill and pay day is Friday.
How does one wear out porcelain?
Don’t install upside down.
Get a taller one with an elongated bowl, they are better all around. It even stops my short dog from taking a dirty drink.
Buy the bigger size wax ring.
Get a permit
Turn off the water to the cistern, flush the toilet, plunger the water in the bowl out as much as possible, wear protective gloves and take precautions to prevent water left in the toilet from spilling everywhere when you remove it.
Then make sure the flange is clean, make sure you have a correct wax ring, ensure the new toilet has the right receptacle for the flange ring you’ve got and fit an extension if you need one.
If all else fails…call a plumber.
Just call a plumber!
Good luck
Don’t get caught doing anything illegal.