Most good drain line repair 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.
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.
In repairing a tub faucet, you will notice that there will be drips that you need to address to. With this, you will need to replace the washers and/or seats.
3) Call the first one you see and give them the job. It is okay to ask plumbers for an initial estimate. If you live in a large, urban area chances are you will have many choices. Don't feel as though you need to hire the first person you contact. Get the information you need, then comparison shop. Check websites and social media accounts to get a feel for how everybody stacks up. Then make the final call.
Check that your plug holes and waste outlets are clear of hair and solidified soap also check the "U" bends or traps under your sinks for potential blockages. Occasionally pour boiling water line repair down your sinks and shower wastes not forgetting the washing machine trap. Look outside too for any weeds or leaves that may be blocking gutters, gully's and waste outlets.
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.
The plumber you hire does not normally do heating but will do hot water heating or in floor heating in the house. Some places you can use the water heater for both domestic hot water and for in floor heating if the heating is a secondary heat. Check with your local plumbing codes on this to be clear.