> Were the people selling/buying drugs on Silk Road top-level drug merchants?This is unknown, but my assumption after looking at transaction records is yes.
> Or were they suburban kids?
I'm not even sure what "suburban kids" means. I think there's a wider demographic of low end product buyers, than what you describe, but yes.
> How did the actual delivery of drugs work?
From public sources, it appears the dealer would typically use prepaid shipping and drop it into a public postal box for delivery.
> And doesn't the government have ways to detect drugs in the mail?
Yes, and it seems like criminals are always one step ahead. I know that this summer, just prior to DPR's arrest that dealers were using some scheme that involved multiple layers of sealed mylar to counter the gov't's detection techniques. Sometimes these bags were stashed inside a figurine or some other object, and sometimes they were slipped inside the pages of a magazine.