Compressor grinding

[MVK]

Hello folks:
I was so proud of my retrofitted AC on my benz. Now its grinding all of a sudden. Tried adding 2 oz of oil no use.
I have 2 Questions.
1. How difficult is it to change the compressor as DIY project.
2. Do you think its ok put a generic bur NEW R4 or should I go and find the AC Delco.


I am not going to put the rebuilt one so dont even go there. Please give me a suggestion to above 2 Q.

Thanks

MVK