In case you want to become a faucet replace through apprenticeship, you will have to approach the local plumber's union, who can help you to find a professional plumber willing to hire an apprenticeship.
When you get to the house stand if front of the toilet and locate the water shut off valve. Should be down below the toilet on the wall. Just turn it off (righty-tighty) completely and flush the toilet. All the water should have left the tank, well at least most of it. If there is remaining water line repair get it out with paper towels or a rag. The important thing is that no more water came in. If it did then your valve is not shut all the way or not working and you need additional help.
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.
Blisters in asphalt or felt roofs only need to be treated if they contain water or have caused the roof covering to leak. Press the blister to check if moisture is expelled. If so, it must be sealed with a patch.
Be certain that the bathroom exhaust fan vents to the outdoors, not into the house or attic. If the exterior vent dampers don't operate properly or water line repair don't seat well have them fixed or replaced.
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.
Over the counter drain cleaning products offer convenience and effective results. However, they are best left to those who need to simply improve the flow of water, not those who need to repair it.