To the first question: Though as one poster correctly said, agencies are going away from 10 codes for interoperability reasons. (ie: different departments use different codes and it can be confusing) However, for some things they will still use them. Also older officers still use them out of habit. Where I work, you probably wouldn't say "There is a dead body at XXX Street. We would still use a code for that.
To the second poster, death notifications vary by department too. In some places a detective or other officer will make the death notification. There are some places where, believe it or not, someone from the Medical Examiners Office does. Typically though it is the police department.
If you are not sure if it is a muder or not, it still gets treated like one. Generally you would try to verify the address (not everyone remembers to update their license!) You try to make the notification in person, but if it is too far away, you can contact the local agency and give them the information and let them handle it.
Death notifications suck. You have to break the news to them and then try to get whatever information you can. (ie: place of work, occupation, friends, enemies, habits, etc, etc) Next of kin can be a useful source of information, but keep in mind you've just given them devestating news and now you are questioning them.
Did I mention death notifications suck?
BLH