Z4 only works on Froyo, not GB; if you're on 2.3.3, don't bother with z4. Google "Pete's Root Tools"; it's a program you run on your PC that roots your phone in a few minutes. Also, if you plan on taking updates OTA in the future, DO NOT remove any apps; get an app like ROM Toolbox or Titanium Backup and freeze them (you have to buy the app for that feature).
Cyanogenmod 7.1 is solid for the D2, but there's an Miui from Galnet that uses ICS features and drastically increases battery life, so if that's something you're interested in, check over at Rootzwiki for the threads and files.
As for tethering, I use EasyTether. Paid version lets you access SSL websites, free version does not.