I just inherited a 1989 Ford Festiva (I love little cars, so it's perfect for me)! The problem is that it's been sitting in a garage for 2-3 years without being used.
What is the smartest way in handling mechanics possibly trying to rip me off? What are the basic things to be done to a car that's been sitting for a long time without being used?
A couple of years off the road really isn't a big deal. The most important concerns will be fluid conditions.
You should start by adding some fresh gasoline to dilute the old stuff currently in the tank, along with the addition of a bottle of fuel treatment. Then change the oil and filter and lube the chassis, preferably before even starting the engine for the first time. Hopefully the battery can be saved with a good charge.
Then a transmission and coolant system service would be recommended. After that it's just a matter of going over the vehicle like any other by checking the tires, brakes, belts, hoses, etc.
You obviously don't have a repair shop that you can trust, so all I can suggest is getting two shops to go over the vehicle and compare their findings, just like a second opinion from the doctor.