Shut off the power to the condenser. A compressor overheats when operated without refrigerant and can shorten its life.
When a system blows out the refrigerant, it typically blows out a good amount of oil with it. A lot of oil in an area is like a giant finger pointing to the problem area..
Repairing coils depend on the skills of the technician, many coils can be repaired, some cannot. Hermetic compressors leaks are not economically repairable.
Most people want a guarantee with the repair and don't want to pay enough to make it worthwhile for a someone to do it and guarantee the work.
I've repaired a coil and the compressor failed two weeks later. I did everything right and didn't take any shortcuts. Still, the 17 year old compressor broke, family was hot again, customer was unhappy with me despite my impeccable work. They'd put a lot of money into previous repairs,
I've repaired them and not had any problems too.
Leaks can be caused by many different things. Nails thrown by lawnmowers, bullet damage, you name it. A factory braze leaks. Vibration caused refrigerant tubing to rub through. Condenser fan goes out, pressure shoot up high enough to pop a weld or section of copper tubing. I've had electrical wires rub through the insulation, short through the refrigerant tubing and melt a hole. Condenser fan blade falls apart or off and chops through the outdoor coil.
Rotting oak leaves ate hole though copper ( 2 different homes within a month). I've seen the compressor leak through a weld on the shell or at the terminal block. I've seen internal electrical arcs blow out a compressor terminal.
Repair or replace? As a technician I check for components that are severely worn and may require repair soon.
Notify home owner of all the issues that are identifiable before making the repair. That way the fully informed home owner can make whatever decision is right for them according to their values and budget. There are always issues that are not identifiable unless the entire system is operating.
Fixing a simple leak, not simple in some cases, a pain in a few.
Repair leak, replace lost oil if significant loss (an educated guess,some systems only had a few ounces to begin with), replace liquid line filter drier to remove water vapor that has been absorbed by or molecularly bonded to the oil during repair. Pressure test the system to make sure repair holds and identify additional leaks.. Repair leak again or fix second or 3rd leak now identified. Pressure test again and repeat cycle until it holds pressure for specified test period. Evacuate system to specified levels of vacuum and see that it holds for the specified period of time. Locate leak and address leak if it doesn't maintain vacuum. Add correct amount of refrigerant after system is tested as leak free.
Test AC operation,
Is it functioning correctly, are there any other issues that need to be addressed. Notify home owner of any additional issues that have been identified.
Some will say I take too many steps in doing repairs. My reply is I fix repairs made by people who never check their work. Most repairs are simple, this lulls people to develop habits which may not serve them well in the long run.
I hope I've been helpful, I do tend to do a brain dump when discussing a subject. A lot was deleted for brevity, believe it or not.