Timeout waiting for ARP/RARP tells me it is trying to boot from the net. Did you try booting from CDROM? Doesn't sound like it succeeded, sounds to me like it tried booting the CD, failed, then tried to boot from the default device, which looks like is the net. Are you trying to boot from a CD or DVD? Does the machines actually have a DVD drive or is it a CD? This is important, if you have a recent solaris install disk, there is a very good chance it is a DVD, which isn't going to do you any good if you don't have a DVD drive. You can download the CD version of solaris from Sun's website. If everything looks correct try doing a boot -r the -r tells it to check for new hardware, then reset it and do a boot cdrom. Still not workiing, the cdrom may not be listed in the devaliases.
Type print-env. That will show you what the boot-device is. It will probably say net.
Type devalias to see what devices it knows about. Your new disk should be there. If it is not there or if there is something else, like an old disk listed, then you need to delete/change the entry to point to your new disk. There should also be an entry for the cdrom.
You can change the aliases using 2 commands, devalias or nvalias. devalias does not persist between reboots, but it is a good idea to test your alias using that so you don't delete/change the wrong thing. Once you have the correct path for your alias set it with nvalias which will store it in the NVRAM. You use the path that is output by the probe-scsi comand (the cdrom might be ide, so try probe-ide also). You need to make sure you have an alias for your disk and your cdrom.
Now type setenv boot-disk disk (or whatever you named the alias for your disk). That sets the default boot device to the disk.
do another boot cdrom.