1. Yes
2. Yes. I paste the following into my crontab as a reminder as to what the order of fields is:
#Crontab field order:
#minute (0-59),
#| hour (0-23),
#| | day of the month (1-31),
#| | | month of the year (1-12),
#| | | | day of the week (0-6 with 0=Sunday).
#| | | | | commands
You edit the crontab using crontab -e and make entries like the following - based on the above:
00 11 * * 0-6 "<script to run>"
This runs the script at 11:00 am every day. Save your crontab using wq!, as in vi.
3. I see no reason why db2 shouldn't be the same as any other database. We use Oracle and make entries of the type:
00 11 * * 0-6 su - oracle -c "<script to run>"
which runs the script under the Oracle user id. You can of course make a crontab for user Oracle or whoever if that's what you prefer. Bear in mind that cron uses a very restricted environment, so it may be necessary to explicitly set environment variables ($PATH etc) within the script itself - this is a common gotcha.
Hope this helps and good luck.