Most good reliable will recommend replacing a gate valve regardless of its condition. The time to discover if it will work is not during a flood in your bathroom. If you have it replaced with a ball valve then check your water heater and laundry valves, too. Have them replaced at the same time with premium ball valves. Ball valve laundry bibbs make it easy to shut off the water to the washer after each use which may help to prevent floods in the future.
The wax ring is used to seal the drain outlet on the bottom of the toilet to the drain opening in the floor. When a toilet is installed, the ring is placed onto the drain... the toilet is dropped onto the ring... and the toilet bolts (also known as closet bolts) are tightened enough to lock the toilet in place. If that wax gasket ring starts to fail or isn't seated properly? Sewer gasses can sneak out from under your toilet causing your bathroom to have that suspicious smell. It can also cause water line repair to escape, sometimes invisibly, with each flush potentially damaging the floor hidden under the toilet.
The con to time well spent is only if the fix or installation works. Suddenly, when a pipe is squirting water or the dishwasher is leaking all over the floor, that time seems wasted instead of well spent. Now your time is wasted, plus you have to pay for a professional plumber to come over and fix the mess. That time could have been spent doing something else, like golfing or swimming or gardening.
Getting advice from someone who has not made any money online is like asking a plumber to shoe a horse when they have never done so. Why in the world would you do this?
These are people who would naturally refer to each other because they typically refer to each other. What about a "Home" referral team? people that support the "home" industry. More people are electing to keep their home and are willing to do the maintaining or fixing up. Electrician, plumber, window, roofer, siding, flooring, and so on. Think about these people getting together once a week to talk about projects that they are working on and creating a water line repair core of competent reliable partners that refer to each other. Inevitably, a person needs carpentry work after the electrician leaves.
When doing the install on a water heater, keep an eye out for unconnected pipes. A commonly missed pipe is the one that leads out from the area for drainage. It is probably a recirculation pipe; that helps your water remain heated without wasting too much water.
A large plumbing job, such as re-piping or installing additional fixtures, may require a permit. Check with your city's department of building and safety before asking for estimates, and avoid any plumbers who are reluctant to comply with regulations.