You must serve a SUB-025 BEFORE you serve the form in any event. If you are in the discovery period and simply looking for "business records", serve SUB-010. If you are asking for records for trial, serve SUB-002. UNLESS the propounding party agrees to service in any other manner, the notice and subpoena must be personally served. It can be served by any third party but the proper proof of service must be prepared and signed by the serving party.
I agree with counsel. Best of luck.
Please note that this answer does not constitute legal advice, and should not be relied on, as each situation is fact specific, and it is not possible to evaluate a legal problem without a comprehensive consultation and review of all the facts and court pleadings filed in the case. This answer does not create an attorney-client relationship.