The IE8 setup procedure should check your existing plugins and carry them over. There is always the possibility that 'some' plugins are not compatible, but IE8 has been out for so long now that they will have been updated.
No need to touch Nortons. It should recognise the new browser. Flash and Java may need reinstalling but they are easy to do if necessary, and you will soon know when you visit a web site that requires either. The web page will tell you.
Currently use IE7
Vista Home premium 32 bit with Vista SP2
Norton Internet Security 2010
If I switch to IE8, then how do the items in the IE7 add ons, such as java, flash player, the intrusion prevention and tool bar with my Norton; Transfer over to IE8?
Do I have to reinstall Java and Flash player? Reinstall my Internet Security?