It's crazy, you have to do a lot of searching and trying to patch together info to figure out how to get the Newtons going in 2010.
For starters, you should just go the easy way - Keyspan USB Serial adapter, a retro serial cable, and the latest Keyspan 10.4 and above drivers and NCX and the 40Hz Dates Fix patch for your Newton.
I also recommend NewtSync which will sync your Address Book! Its fantastic:
http://www.thenowhereman.com/hacks/newton/
Then you can use the Newton today.
It's a bit of work but the Newton OS can still work and its great as a GTD PDA if you're clever. Try Adam Tow's NewtToDo and use the folders as contexts ;o}