What age is system including air handler?

Your service tech/dealer did you no favor both in price and quality of the service you received. A typical gas n go shows a tech/dealer of questionable ethics.

Sorry. This is the truth.

IMO

8 years old this April, can you replace the evaporator coils? The first technician also found leaking at the outside valve.

Twee

I would get a second opinion. Leaks at a valve are usually easy and relatively inexpensive to repair.

Evap coil leaks In an air handler can be another matter entirely. Standard procedure when adding refrigerant is to include dye especially when tech did not attempt to find the leak. Let the system then run for several days and return to check
coil to locate leak with proper tools. Was dye inserted? Do you even know?

Yes, evap coils can be replaced in an air handler. However, usually this s not cost effective due to the expense. I assume air handler is out of warranty.

IMO

Yes you can just replace a evap coil whether it's electric or gas appliance.
When was the last time you put freon in the unit? If never I would see how long charge lasts if every couple months time for new equipment unless leak is at solder point. If there was a leak at shreader vlv. then that should fix it unless tech is guessing at leaky evap coil. Did he check with sniffer or bubbles?

tweedge,

Shrader valve should be an easy job with shrader valve core removal. probably a 5 mins job. Leaky evaporater coil is totally a different story. Yes if it is leaking at the evaporater coil, it's better to replace the air handler due to the labor involved in replacement the evap coil itself. The question is it leaking at the evap coil? did you see any kind of proof?