I am replacing the a/c system in my 1998 Honda Civic DX. I plan to replace the compressor, condenser, drier, expansion valve, and one pipe/line (because I cracked it by accident).
Finally got around to replacing the expansion valve, which is housed in the same assembly as the evaporator. The evaporator has a lot of metal fins that are bent, and some of the spaces between the metal fins are full of yard debris.
As far as I know, the evaporator functions. My a/c compressor locked up and potentially released a bunch of metal shards in the system. That’s I am replacing nearly everything.
My understanding is the evaporator should only be replaced when it’s leaking, or in terrible shape. Will it be okay? What should I look for?
By the way, getting to the evaporator/expansion valve was TERRIBLE! Very stressful 
If the compressor went and there’s metal in the system, I’d replace the evaporator, too. Why gamble? You’ve got the whole thing apart. Now’s the time to replace it rather than wait and have to tear it all apart again.
As an option, perhaps you could have the evaporator cleaned and tested for leaks by an automotive AC shop.
I wouldn’t reuse it unless I was sure it was in good shape. “As far as I know” isn’t good enough.
Since you’re rebuilding the rest of the system in its entirety, it would make sense to replace the evaporator too.
I agree with McP; why gamble?
When a compressor fails where debris is deposited throughtout the system, the components don’t require replacing, but they do need to be flushed out. A DIY’er can get a flushing gun such as this, http://www.amazon.com/Robinair-17595-Flush-Gun-Kit/dp/B000O1A4HY fill it with the flushing agent, charge the bottle with compressed air and blast out the debris from the components. It’s a lot cheaper than replacing everything!
Tester
Perhaps you must replace your evaporator when you smell something bad inside your car when the air conditioner is on.This will just mean that the evaporator is clogged.