NES World used to (and probably still does, since Martin archives EVERYTHING) have interviews with some real programmers and graphic designers that worked at large and small companies doing NES titles.
Historically, Nintendo has never assisted in providing ANY tools for developers. They've given whoever signs up with them a developers manual, which goes over things like registers and memory maps, but is VERY badly translated from Japanese (more than likely translated by a Japanese native who has a semi-okay grasp of tech-savvy English). You received no hardware tools, no software tools, no nothing. This was most definitely the case with the SNES.
It's safe to say that the NES was more than likely the same way, especially when you look at how video games were developed in the late 80s -- and still are today. Gruelling hours, very little pay, non-regular paycheques, high stress, and very little debug time. A perfect example of the "SHIP IT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!" mentality that is still used in tens of thousands of companies in the United States and Asias today.
I personally have only run into one individual who has claimed to have the official Nintendo developers manual (register docs, memory map, diagram photos of how the PPU interacts with the electron gun (i.e. doesn't), yadda yadda), but he flat-out refused to send it to me or even take a couple photos of it, simply based on the motive that he wanted to gain something from it (recognition, or something like that) rather than just give it out -- because he knew if he gave it out, it'd be released all over the 'net and no one would give a fuck who he was and how he bent over backwards to get his hands on it. Pretty justified stance, if you ask me.
A footnote: I wouldn't recommending requesting things like this, especially on a public forum. Nintendo is now working NES games back into their profitable market value by coming up with the eReader thing for the GBA. Right now you can only play non-mapper games on it, but it's likely that they'll try to push this thing further, since it ensures that they have some legal standing in court over ROM piracy and what not. These games which are non-profitable to them are now becoming re-profitable; they're being dug up out of the back storage bins of Nintendo to be re-released, which means that in court they could indeed defend that illegal distribution of *anything* NES-oriented is affecting their income as a company. There's no proof of this, however; it's just an idea of mine.