I can help out with the bitcrushing stuff, it's an effect I use all the time, your simplest route is to just use a VST plugin in FL Studio (or anything that handles VST plugins) to generate the effect.
(for the record though, this is
simulating the effect and not actually digitizing the analogue audio, if you're just looking to mimic the sound without worrying about hardware and platform limitations this is infinitely quicker and easier)
My current favourite is E-Phonics LOFI plugin, I like this one just because it's super quick to drop in and play with, and bonus points for being free;
http://e-phonic.com/plugins/
(It's right at the bottom, the one without a screenshot or even a description, I think they're embarrassed they made something interesting rather than yet another drum synth or tape-delay effect.)
There's also dBlue's Glitch and Crusher plugins, never used the dedicated Crusher, but the Glitch plugin contains a nice and accurate bitcrusher effect, just be sure to set it to solo. Bonus points again because it's free;
http://illformed.org/
(all the older plugins come in a zip, right at the bottom)
dBlue is probably your better bet for getting an authentic sound, since you can accurately set the bitrate, the e-phonics plugin is more loose and better equipped for style over accuracy.
The main advantage of working this way is that you get to make adjustments and hear the results as you go, if you're looking to end up with a file you could
actually slap on a cartridge, I'm pretty sure Audacity will let you change the bitrate in the options, then it's a case of exporting/converting to the right format and specs.
I should tell you though, the difference between 16-bit audio and pretty much whatever you'd call "high quality" audio is really nothing, you can't really hear the difference in practical terms. 16-bit is CD quality, so you're gonna want to go a lot lower than that with bitcrushing. The reason digitized speech on old games sounded the way it did was because of size limitations, a 16-bit file is way too big to be practical, you've got to compress that as low as you can go to get a real "RISE FROM YOUR GRAVE" going on.