These things always end in tears...
Information on programming for the Nintendo 64 tends to be fairly thin on the ground - which is understandable, because Nintendo are an extremely proprietary company, the N64 was (and is still considered to be) an extremely complex beast (you would have a far easier time writing PS1, GCN and Xbox games), and we're 2 generations past it now. Developers typically devised custom formats for all sorts of data in their games (file formats, text formats and the like), and ofcourse directly manipulated an extremely complex and I'll add
dynamic hardware platform on the lowest levels (machine code/assembly,
microcode) to write their games. For these reasons, N64 game programming tends to be nowhere near as cushy as writing games on other platforms, and certainly a far stretch from PC game development.
That said, I'd stick with Neildo_64's advice - you will need to learn how to develop a game in the first place before you start complicating the process with MIPS assembly, leaked technical specifications and format details reverse-engineered by underground homebrew scenes. You'll learn as you go? You'll spend a good year or so learning before you even get an N64 to print "Hello world!" to the screen - if you're particularly gifted, and lucky.
For your current experience, I tend to point everyone in the following direction, but
Steve Heller should be able to help you - particularly his book,
C++: A Dialog, which is geared towards absolute beginners but picks up in pace very quickly. C++ probably isn't directly relevant to N64 programming, however since I've never actually found an N64 compiler, C probably isn't going to be a lot more useful either. However, C++: A Dialog will give you a good introduction to programming in the high level, and a good general understanding of what's going on at the low level on any platform. If you don't understand how computers behave on the low level in general, you have no hope of taking on the N64.
Anyway, I might start digging soon, and see what information on the hardware and possibly programming utilities I can dig up. Me and a friend have been dabbling in the thought of working on an N64 emulator as a long-term undertaking, so I'm going to have to look this stuff up anyway. More soon.