It can seem like a lot of work to learn about plumbing, but with some research and effort, you can educate yourself on the subject.
Have a professional flush your septic tank cleaned every five years or so to keep it in prime condition. Although it is somewhat of an expense to pump out a septic tank, cleaning up sewage backup in your home will ultimately cost much more.
Do not pay anything until they finish the problem is fixed. You may have to put money down before they start working, though you should not pay the full cost until you can be certain that the job was done correctly. You should know the plumber did his job before they get your money.