Hi,
If you change the account name/password, you will have to change it on all your other servers, if you have multiple site backup servers. For Remote Agents, no change unless you change the name of your server, or use the FQDN, instead of just the name. If it was backupserver.internal, and it's now backupserver.local for example, your Remote Agents probably won't publish themselves correctly which will cause issues with your backups.
If you're doing cross-domain backups, it's a bit tricky. I managed to get our CASO server to detect another backup server in a child domain by doing the following:
1. On remote server, add an entry for my CASO server into the hosts file.
2. On the CASO server, I did the same as in 1, and then added in that child domain's service account for Backup Exec.
3. On the remote server, I was able to browse the CASO server, and once I could do that, could add it onto the CASO server.
That's about all I can think of.