Couple things to be aware of:
1. You do not have to run sql under a dedicated service account (although
from a security standpoint, you should). I just want you to realize that it
isn't a technical requirement for SharePoint to run, running SQL as the
local system will work.
2. You don't have to setup a SPNs in order for SharePoint to work either.
You will only need SPNs if you will be having SQL server pass through
windows authentication from SQL server to another physical box. For example,
if I login to SQL Server using windows authentication and then run a stored
proc or use something that connects to a seperate physical box AND attempts
to pass the same login credentials to the remote box as I used to login to
the initial SQL server.
Depending on your environment, you may find this is either very rare or
never happens (it never happens in my environment).
I just wanted to clarify that you do not always need to have SPNs setup,
especially for SQL. I find in my environments that I need to have SPNs setup
for the app pool accounts in IIS on the WFE servers, which is something I
didn't see in the document you linked to. The reason for that is if I have
user logged into MOSS on WFE and then wants to connect to excel services on
a different box, it needs to pass his credentials over to the excel services
box, which requires an SPN to be setup for the app pool account on the WFE.
Basically, any time you have windows authentication attempting to be used
and it involves multiple servers using a chain of requests (server 1 >
server 2 > server 3) then you will need an SPN setup for whatever service
account is making the request on server 2. In more complex scenarios such as
(server 1 > server 2 > server 3 > server 4) then you need SPNs setup for the
service accounts on server 2 and server 3.
I just bring this up so hopefully you can understand a little more about why
and when you need an SPN rather than just creating one because the
documentation says so.
Back to your original question, creating the SPN for SQL is very easy:
1. Get the setspn.exe utility by downloading "Windows Server 2003 Support
Tools" (google it)
2. Run "setspn.exe -A MSSQLSvc/<SQL Server Computer Name>:1433 <NT
Domain>\<SQL Server Service Account>"
3. Open the "Active Directory Users and Computers" Tool
4. Locate the <SQL Server Service Account> user, open up properties, and
on the "Account" tab make sure "Account is trusted for delegation" is
checked and then hit OK.
5. While still in the AD Users & Computers tool, locate the SQL Server
computer, open up properties, and make sure "Trust computer for delegation"
on the General tab.
Here [1] is a link to a great article that is far more in-depth that the
info I have provided.