It's a pay upgrade - though there is a small discount for owners of previous versions (that didn't buy a retail version during the qualifying period)
http://www.nero.com/en/631925694661882.html
So if you want Version 6, rake out the old OEM version you got with a burner, it's your ticket to a discount. Best discount seems to be for the download + serial.
Not sure about DVD - I don't have one, so the option (in 5.5.10.42) is greyed out - so it can do DVD, but what it does, no idea.
If it's a BUNDLE version, it will not accept a different drive unless you buy an upgrade key - in which case, you may as well go to V6.
If you buy a retail boxed drive, it should have suitable software anyway.