Hi Milazzo, I have performed a similiar upgrade from a 3050 cluster to a 3170 cluster. There are a lot more details to the upgrade than I've listed below but these are some big points that you'll need to cover.
1. Yes, the lun serials will change and you'll need to revert them back to the originals before you try to reconnect you clients. There are two scripts that I know of on the netapp communities page that help automate this. One for windows (vbs): http://communities.netapp.com/docs/DOC-1754 One for unix (or win too I guess, perl. I wrote this one): http://communities.netapp.com/docs/DOC-2369
2. You'll need to update your /etc/rc file ahead of time to deal with any network card name changes that may occur.
3. Yes, you'll need to reassign the disks to the new head. You do this in maintenance mode and with the "disk reassign" command.
4. You'll need to clear out the old mailboxes in maint mode also. mailbox destroy local mailbox destroy partner
5. You'll also want to make sure that your iscsi and fcp target nodenames are the same after the upgrade. You can do this with the "iscsi nodename" and "fcp nodename" commands.
6. You'll also want to make sure that the hardware model you are upgrading to uses the same version of OnTap that you are running on your current head, otherwise you'll need to upgrade that too.
If you'd like email me privately and I can get you a copy of my upgrade guide I used for my own upgrade.
Romeo