You'll need a pressure regulator and flow regulator, the simplest approach is to buy a regulator that does both. You can use an argon flow meter with nitrogen, but argon is heavier than nitrogen so you'll have to mulitply the meter reading by a conversion factor. I included the table of conversion values here:
I just thought I'd share a description of the gear I put together for inert gas asphyxiation with nitrogen and an exit bag. It's pretty basic since I felt it would be better to start with something simple and functional, then upgrade to SCBA/SCUBA or something else in the future if I have time...
sanctioned-suicide.net
Attaching the plastic tube isn't a problem, you use a barbed fitting with a hose clamp and it's very secure. These aren't ordinary threaded fittings, they're specialized for inert gas so you have to get them from a supply house or online if it's not included with the regulator. There are more detalis about the fittings in the link above.