What parts did he replace? Compressor is not a serviceable item and i have never heard of anything like opened the compressor and changed parts. Did you mean he opened up the clutch assembly?
First confirm if the noise is coming from inside the compressor or the clutch mechanism (use a mechanic's steth or a long piece of metal rod, carefully place one end on compressor casing and one end touching your ear). How is the cooling of car? Ask him to remove the belt and move the pulley, is there play in it? if yes, remove the pulley and check bearing, My guess is that the pulley bearing is shot, change it with a new one asap otherwise like in my case, it will bite on to the casing rendering whole compressor useless.
if pulley has play but bearing is fine, then you gotta replace the compressor.
If pulley has no play, check if clutch has play, if both the clutch and pulley are fine, then your compressor is gone.
New compressor costs ~30k
kabli costs 6.5K
Regarding reliability, you can test before installing if the pulley moves without any noise, no wobbling etc but there are no guarantees, It can last of years or it can give up any time. Usually mechanics give 15 days warranty for kabli compressors so ask your mechanic about it.
Avoid using AC until you fix it, i was unaware of the real issue and i kept using AC with the noise and one day it bite on compressor casing, tore the belt in center. Even though my AC was working great, i had to dump it all together and buy a kabli one. Ultimately it costed me 10000, if i had replaced bearing in timely manner, it would have been a mere 2-3k job.
And all work stated above can be done without removing compressor or even gas. Don't let mechanic fool you