If you got more then 50000km out of it you are lucky.From EF to EL the compressors have a very common problem for becoming noisy which turns into a rattle then complete lock-up.The internals of the compressor either the rotating vane or the fixed vane breaks and thus locks it up sometimes actually cracking the case,like throwing a rod so to speak.Worse case it locks up causing the WAC relay(part of series of relays to supply power to ECU) to blow and then the engine won't start and the worse part you can't remove the belt with out lossing drive in the power steerin,water pump and alternator.
$800 is about right,$650 is the going rate for an aftermarket compressor which is the same as the genuine unit but in a different box.If the compressor is noisy it my also need a flush out and dryer, worse case if metal is in the system.If it is not that noisy then get in quick before it causes major damage.
A Au compressor is totally different in design using piston type set-up compared to the vane,the manifold setup is also different,so to answer your question no you can't swap them.
On another note for some strange reason when the EA-ED's esently same design (vane) that hardly do break internally even when there completly out of oil they still work after some oil added.It must be due the fact they used cheaper alloy metal.
QLD REP 4 EA-ED club.