Hi fifty50,
If you want to assist the kind of photographers you're talking about, you need to build a little network for yourself. Try to approach first assistants and studio managers - they will be the ones who get the calls and emails - unless you have an opportunity to approach a photographer in person. Maybe you can get friendly with some people at Milk Studios or Pier 59, that's where all the action is.
On the digital side, you should learn Phase One C1 Pro software (go to the Phase One site, download a trial version, look at the tutorials, practice, etc) and familiarise yourself with shooting tethered, but more to the point, learn not just about shooting, but workflow (through to archiving). This will make you much more valuable as an assistant, not to mention help your shooting out a lot. Also make sure you can load 8x10" and RZ film super-quick.