If you mean the difference between 'part' and 'a part', then I'd say that, here, the omission of the indefinite article brings the person closer to whatever it is that they want to be involved in. If you're part, you're in the flow of things together with all the others as one. If you're 'a part', it is more delineated and defined and not, presumably, as exciting. It would be OK with the article, though. Ron's right about the word 'say' not making sense there.
