Troubleshooting - ODS and alternate boot
FYI- you stated you run Solaris 8 - that comes with DiskSuite (also known as ODS)
The metastat, metattach, ... commands are in /usr/sbin. If you don't use it, then you would have to do a ufsdump of the root disk onto another, install the boot block, and then update every so often with ufsdump (you would still need to do any steps to know what the device is, set up a devalias for that disk to boot from).