You may be uneasy about dealing with car repair shops. A major reason for this might be a bad past experience. Most likely that experience was about a final bill that was larger than you expected. Those expectations could have been wrong, or the mechanic could have been a vampire, trying to suck your blood dry.
The estimates could have been faulty if they were based on either a friend's guess as to what the work should cost, with no estimate from the shop, or the original estimate from the shop was too low, which is a trick used by vampires.
Regardless of the source of the bad information, it was a mistake that should have been avoided, and it's not that hard to avoid it. Let's chase it through the woods a little first, with some boring background information, then we'll drive a wooden stake in the heart of the beast, should that be necessary. Don't be afraid. You can do this in three steps.
The first step is to ignore all guesstimates from your friends. They are well-meaning people trying to impress you with their expertise, but unless they have recently had the exact same problem as yours -in exactly the same year, make and model of car, with the exact same engine size- they can't have a clue about what your problem should cost. They might think that all water pumps jobs, for instance, cost about the same. They don't. For instance, on a 2004 Dodge Caravan with a 3.8 liter engine, a water pump job is a one-hour job. If that same vehicle has the 3.0 liter engine, the water pump job is a four-hour job. Your friend cannot know these details. The techs doing the work every day don't necessarily know either, but they have the resources to look these things up.
That brings us to the heart of the problem, knowing what the job should cost. Most jobs are listed in "flat rate" manuals or on-line data bases. Those times multiplied by the labor rate of the shop in question, plus the price of the parts and materials, equals the price of the job. A reputable shop will look up all of these things before giving you an estimate. Don't ask them to give you a "ball park" estimate before they look it up. You're just asking to be misled. If their guess is low, you will think they tricked you; if it is high, you will think they tried to overcharge you. Let them look things up, and then give you a firm estimate to which they can stick.
The second step is to know your rights. In Florida every garage is required by law to have you sign a notice that says you have a right to an estimate, and the shop cannot exceed that estimate by more than 10 percent without your consent, or you can waive your right to an estimate. Other repair services, like plumbing, electrical, boat or air conditioning repair, etc, do not have these protections. However, many of these other repair services have a feature that garages lack. Many of them require state licenses to practice their trade, requiring testing, which shows (some) proof of competency. Automotive mechanics are not licensed. This means that any numbskull can say he's a mechanic and go into business.
Therefore, the third step is to verify the competency of those with whom you are dealing. Although they are not licensed, mechanics can, and should, be tested and certified by the ASE organization, (Automotive Service Excellence) and/or a car manufacturing company. Also, all garages are required to be registered with the state, county and town in which they do business. This keeps them under the thumbs of consumer protection agencies and environmental protection agencies. This is for your benefit, not theirs. Look for signs showing certifications and registrations before trusting your repairs to any shop. These things don't guarantee a trouble free experience, but dealing with someone lacking these things almost certainly guarantees a bad one. You might even have to use that wooden stake.