In the federal audit world, the CPA will definitely make you stand out as a job candidate.  My current employer places a lot of emphasis on professional certification, particularly the CPA.  I'd guess at least 30% of the auditors in my office are CPAs.  My previous employer barely did any financial audits, and there was little to no emphasis on professional development; maybe 10% of the auditors there were CPAs.  CPAs get a lot of respect, but at the same time there are quite a few people with years of experience but no certification who don't think a lot of the CPA designation.

At the places I've worked, the people who make hiring decisions are the audit managers and audit directors - NOT the HR people.  The places I've worked have not had dedicated recruiters; managers and staff act as recruiters at job fairs, and HR takes care of the administrative side of things.

My guess is that an employment gap is not going to be a major issue for most government HR or hiring managers, but I really don't know. 

OIGOA -

In my opinion, the certifications that stand out in the government are largely the same ones that stand out outside the government - CPA, CISA, CIA.  (I suspect that there is a growing need for CISAs, since many government agencies are starting to do FISCAM audits, FISMA audits, and SAS 70/88 reviews of their IT systems.)  The Certified Government Financial Manager (CGFM) certification is quite popular within government.  The CGFM is sponsored by the Association of Government Accountants (AGA); involvement with AGA is encouraged at my organization, and it would probably be a resume boost as well. 

Many agencies are now outsourcing audit work to independent public accountants (IPAs), and contractor supervision is becoming a big part of the job, particularly with financial statement audits and IT audits.  Consequently, project management training and experience is going to be a selling point on resumes.  There's a Project Management Professional (PMP) certification that's sponsored by the Project Management Institute (PMI); my organization is starting to put emphasis on that certification for current employees.

Bubzeebub -

Federal job listings are called "job announcements," and they are typically open for a certain period of time, usually around a month.  (Some job announcements are open indefinitely.)  After the closing date on the job announcement, I'd say takes one month for them to call people for interviews.  If it's November or December, expect to wait two months.  I understand that applications are given a numeric rating, and usually the selecting officials pick the three best-qualified candidates (based on the numeric rating) to interview.  Some agencies hire for a number of positions at a time; I believe the interview process may work a little differently there.  The selecting officials then decide which candidate(s) will receive job offers, and Human Resources calls or emails with job offers.

Unfortunately the government does not do a good job of following up with people who aren't selected for interviews or jobs.  I've probably applied for a couple dozen positions.  Most of the time I get a confirmation that they've received my application.  About half of the time I've gotten notification that I was or was not selected for an interview.  (For what it's worth, I got called for interviews for 3 of the 12 jobs I applied for - this was before I started the CPA.)  I interviewed for 2 jobs but didn't get an offer from either; only 1 called to tell me.)

After you get the job offer, there's a ton of paperwork to be done, and sometimes background checks.  For both of my jobs, it took about 2 months from the job offer to the start date.