New to lenny/sid need advice

["raman narasimhan" <ramsn88@gmail.com>]

i've newly switched from etch to lenny/sid.. i did a smart upgrade of my system.. how do i ensure that no configuration conflicts occur when i install or remove a package??? i cant install packages like Kinfo contol center.... which i used a lot in etch..

also when i install a lenny/sid package, what happens to the old etch package?? is it removed or still there???