The fact that you're a neighbor is a good thing as it means you will probably follow the case. I suspect as you do, and this moves through court, you'll gain a little more insight into what may have been going on right under your nose. I suspect you'll find that the police that investigated this case had their ducks in a row before they charged him. It's really not uncommon for someone to be a little reluctant to talk about being sexually abused as a child, particularly when the abuser is such a popular figure in the neighborhood or church. That said, your neighbor ought to be considered innocent until proven otherwise. Just keep us posted on your thoughts as you find out more about what's been going on over there.
Well, I think that when you review the trial transcript (or plea arrangement) you'll be a bit surprised. They have the ability to track internet activity from a given IP address (to the specific house) where he would have used the computer(s) in question. And what's ". . . an unknown seller that happened to have been previously tracked" mean? That's just a tad shy of the dog ate my homework.
As to his turning himself in, there was an arrest warrant issued. Had he not, he most certainly been hunted down and brought in at a time much less convenient that the opportunity they gave him to surrender.
As to his chance to defend himself, well he'll get that in Kent County Circuit Court and Federal Court soon enough. You may be well advised to find someone else with a better version of the story.
I don't doubt he made some contributions, and some may have been good, but lets not be to quick to assume that he got caught by mistake. The people that caught him are extremely comprehensive and it's very possible he's been at this for a very long time, but finally identified. We may never know, but if you read the report, you'll see that the tips were going into a national hot line from all over the country. That doesn't happen just because he bought a computer off of e-bay. That requires active participation.