It's discussed many times already here.
May be first have a look at available documentation on the net, e.g. https://docs.jboss.org/author/display/AS71/Developer+Guide#DeveloperGuide-HowdoImigratemyapplicationfromJBossAS5orAS6toJBossAS7%3F.
Any concrete problems you have?
does that apply for JBoss 4.x (4.2.3.GA) too? (after having read the title, i went straight to google for some other more specific guide 4.2.3->7)
we are now planning to migrate from jboss 4 to jboss 7. i found this thread. i have same question as you had back in august 2012. does the document applicable to move from jboss 4 to jboss 7? also, can you please share any important documents, check points to take care? I am a newbie to java/jboss world.. Thanks. hope you had a successful migration..