[TYPO3-mvc] Extbase migration 1.3 -> 6.2

[Jan Kornblum]

Dear newsgroup,

i've got some questions about migrating extbase extensions from 1.3 to 
6.2:

With TYPO3 6.2 LTS the old non-namespaced variants still work. Is there 
anything special to be aware of when switching to the namespaced 
variante?

Can the modifications be done on an installed extension (in a 
development environment)? Or do i need to deinstall the extension, make 
the modifications, and after this install it again? Just because the 
was no "vendor" in 1.3 and i don't know if changing the 
"configurePlugin()" in ext_localconf would make problems?

Are there any other important things to be aware of when migrating from 
1.3 to 6.2?

Kind regards, Jan