Any HVAC experts want to weigh in on something...

[nstygma]

i think the term you were looking for is compressor.
how do you know the leak is in the a-coil and not some other place?

so you've got a 4ton unit with 3/8 & 7/8 lines. wholesale price from Johnstone Supply for an uncased coil for that is basically $415 and a new 410a copeland scroll compressor is $820. so much hassle to replace them though, then what if it doesn't work properly?

better to have peace of mind for the next decade+ with a new system & warranty.