Nearly $700 for "front brake service"? What are they going to do, gold-plate all the parts? Almost $300 to change coolant? Over $400 for fan belt and tensioner? Etc. Sounds like stealership pricing. 

If the brakes really need servicing that would be the most important thing but I'd get a quote from a good independent mechanic for these items. (A different mechanic if the one quoting these is the one that did the inspection.) Those prices are nuts.

Find another mechanic to inspect the car. 

Outrageous!  $2757 in repairs on a car that costs $20K?  This has got to be a bad joke.

Even if each of these repairs is needed, as Chuck Tobias stated..."those prices are nuts." Indeed they sound like dealership prices and they are notorious especially(in my experience) for recommending brake service way before it is needed. But if the brakes are in need of service, they are priority # 1. What good is it for a car to run if you cannot stop it!?

Last year, I had brake service performed on my 2004 Toyota Avalon at an independent brake and alignment shop. Front and rear Akebono disc brake pads and rotors turned for $300. ($140 total for the pads at NAPA and $160 for labor). And they included flushing the brake fluid. 

The quote for just the front brakes on your car is $693 and $222 to flush the fluid, for a total of $915. Compare that to the $300 total for all four brakes on my car. 

Two years ago, I had the AC recharged for $75 at a local Auto Air Conditioning shop, and have had no problems since. And I live in Southern California, the land of high prices! You were quoted $309, I suppose for the same service.?

As the others have advised, you should definitely take it to a different mechanic and definitely not the dealership for a more honest inspection and estimate.

As far as the 20k price tag, you could check with sites such as carfax, edmunds maybe even auto trader just to compare prices.

Posted by: @mword23

Which Repair on this list is most Urgent?

Brakes obviously.

The inspection sounds suspicious. Most of these things are regular maintenance items. Either the previous owner completely neglected the car (in which case you should run away from it), or the shop wants to take you to the cleaners.  Try to dig up the service history (directly from owner, or from Mazda, carfax etc.).

• Engine Oil Pan Replacement (rusted, slight leak of oil): $525

how bad is the rust? How bad is the leak? Did you take photos?

• AC:  $309

You can test the AC yourself can't you?