How is a flush toilet overflow pipe connected? Can it be easily replaced? I'm guessing it is screwed into the bottom of the tank, but I'm not going to chance breaking something by attempting to remove it until I know what I'm doing.

Hi Bill...

If the toilet is less than 25 years old most likely you have a plastic overflow tube and that means that you'll need to remove the entire toilet tank to get to the nut that holds the FLUSH VALVE ASSEMBLY (with overflow tube) in place... see images.

If you replace the flush valve don't forget to get some new toilet tank bolts as well... ;)

Mark

How is a flush toilet overflow pipe connected?
Mark gave you a excellent explorations of a flush valve,m (see image)
In addition to new tank bolts also pick up a spud washer and a spud wrench,(see images). Be sure, when you tighten down the tank bolts that you leave 1/4" of rock to the tank. If you tighten the tank down tight and some one leans back it can put a strain on the bolts and fracture the tanks floor causing a leak. Good luck, Tom