In case you want to become a water softener 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.
If you bought the same unit it should line right up, if you were unable, you will need to remove or add length to the existing piping. This may require you to splice together copper with plastic, don't let this scare you the hardware store will have all of the necessary parts.
Working on the gas lines is also a complex job that only a licensed plumber can handle because it is very dangerous. Small leaks can't always be detected by odor alone, but a licensed professional has the proper equipment that's needed to ensure that you don't have any leaks in the line.
If the area around the fan isn't clean and dry, or if dust or any sort of growth has accumulated on the blades or inside the exhaust duct, it may be a warning sign of excess moisture build-up. Clean the water line repair fan and area well. Then double- check that the fan is operating properly.
People who own rental properties are great ones to give you information. With all of the service people needed for maintenance on their units, they typically know who to call and what level of work they perform. Most property owners will be more than happy to give you the information you seek. In fact, they were probably in your shoes at one time.
Then, you can take your new shower parts home and reinstall them in the inner assembly. It is very important that everything be aligned properly and tightened to prevent leaks. Beware of over tightening, however, since this can also cause problems. Once you are sure everything is installed properly, replace the cover plate and turn the water back on to test your repair work. With a little bit of work, your do-it-yourself shower repair project can be a success. It does not take an expert, just a little effort and know how.