For a reliable fix, I'd suggest starting with the most pressing issue first, like any major leaks or blockages. Make sure the plumber you hire is licensed and experienced with similar problems. A good approach is to get a few quotes and ask for references to ensure the plumber has a track record of quality work.
I recently found a service called Trusted Local Plumbers in Sydney, and they seem to have a great reputation for reliability. Given your need for a trustworthy professional, this could be a good place to start. Their network includes licensed plumbers who are highly recommended for various home repairs, so you might want to check them out if you're looking for a
local Sydney plumber