RK- IMO. as long as the stock arms are not rotted or bent they can be reused. I always clean and then check the arms when I have them apart to be sure they're ok.
I have not used any AM billet arms so I couldn't say if they're worth the added expense or not. I have found the stock arms or the USA made replacement arms to handle most applications.
I rebuild units vs exchanging. I'd rather work with someone and their original parts. That way they know what they sent me is what they get back. Some of the exchange units I've seen had issues with QC in certain areas. This was not limited to one vendor either.
I recommend you take your time and get your suspensions apart and then make a judgement after inspection.
Good luck with your project, if you need any help let me know.