Ok guys go gentle on me but there area couple of questions that i am not sure about and through looking through here i couldn't find the answers yet.

Firstly , having gained the wisdom on frame numbers and models on an earlier post i now realise i have a MC18 mk1 R2J. Question is i've seen lots of referances to different versions within this ie R4J. Are a lot of the parts for these models interchangable?
Secondly, I was missing the CDI and have mananged to find one marked as PGM. I also have an oppertunity to purchase another one but this is PGM2, they are supposed to be both for a MC18 so i am a little confused. Is PGM just Honda speak for CDI and will both fit?

Probably a simple question but i am fairly new to NSR's and dont want to buy the wrong stuff.