A/C Compressor clutch went, I think

[Ken]

I noticed my A/C wasnt working coming home on a long trip, So I checked it out today and it looks like right in front of the pully there are two pieces that should be together it looks like with rivets, It looks like they have come apart you can tell because one spings without the other and you can see where the head of the rivet has been rubbing the other part. My first question is this part of the clutch and secondly is it tough to change. I did see from searching that a couple guys got a clutch from napa how good is that clutch thanks