When the TRO goes, it will be removed from the (California Law Enforcement Telecommunications System), and will simply be gone. It will not be on any of your records, and no background search will find it. Chances are the judge won't dismiss with prejudice simply because the petitioner doesn't show up once, although the TRO and action will lapse. That makes sense, since the Court won't know why they aren't there.
What you really need to worry about is your ex showing up and you not being ready. It may not be wise to assume they are going to drop it, only to see them show with witnesses and other proof. Be prepared.
The order will be vacated, and the matter dismissed. If the ex-spouse raises new allegations, she can, of course, re-file. The record will not be sealed, nor is there any practical way to seal it.
The case records will be kept for however many years required -- however these court records will/should reflect that the TRO was dismissed against you on X date. You might want to get a court certified copy of the dismissal or the minute order to keep on you in case you ever have to address this issue with a future potential employer.
About your concerns about possible future employment with the government -- I've worked for the government in the past, would look forward to it again in the future, and have many friends that still do. The best advice you should keep in mind is - tell the truth! It is much better to tell the truth upfront, than to have it discovered years down the line that you lied in an interview.
The answer above is provided for informational use only. One should not act or refrain to act solely based on the information provided. No attorney/client relationship is created unless an Agreement is signed by the attorney and the client.