From what I understand, you need to delete all records over 48 hours, but do you have to that at a specified time interval ? Because if that is the case, then the trigger during a insert can be ruled out unless you insert records every day.
I am not sure about the dbms_job package. You could write a small daemon in Pro*C that wakes up every day in the morning and does the cleanup job, else on a unix box, you can put an entry in the chron jobs and have it run at a specific time.
I think there is a place in Oracle too, where you can specify it, but I am not sure on the name of the file.