wilt

Why are you replacing coil?

What age is your AC?

Suggest you get another quote before proceeding.

Price includes recharging?

IMO

The AC is very old, at least 15 years old. The unit is enclosed in the "blower" part of our furnace (located in a small closet) (not the outside heatpump) and when he took off the cover we saw standing water and rust. This indicates the coil is leaking water I suppose. Thoughts?

wilt am

This repair would not be cost effective considering age of old system.

You should replace everything both inside air handler and outside condenser.

these are the minimum specs you should be looking for.
both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF
best matching VS air handler
full BTUs in both cooling and heating for your rated size
R-410a refrigerant(same as Puron)
scroll compressor preferred
electronic demand defrost preferred
thermostat with "dehumidify on demand" feature
staged backup heat strips
new and correctly sized refrigerant lineset
10 yr warranty on parts and compressor

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

My personal recommendation is Trane/AmStd, Rudd/Rheem, and Carrier/Bryant.

Depending on your location, I would not purchase a new system that did not have electronic demand defrost.

IMO