Changing Target Markets - Advice Requested

Howdy...

I'm an independant PI working south central/south western Virginia,
mostly working claims investigations and insurance audits. As I've been
providing almost strictly B2B services, almost all of my business comes
through networking, trade organizations, referrals, direct mail campaigns
and a (sad) few hits from search engines. I haven't a yellow pages ad
anywhere, and wouldn't know how to go about getting one (wherein lies
part of my problem).

I've been pleased with my business to date, but the market I've been
working has been steadily diminishing due to saturation by low rate
inexperienced competition. Insurance is a cut-throat market anyway, so
I'm considering changing targets altogether and moving into domestic
and/or criminal investigation work (I've got experience in these areas).
The criminal investigation work shouldn't be too hard to market since I
can use the same techniques with the legal community that I'm accustomed
to using with insurance (B2B).

But, the region is saturated with competition so I'll likely end up
working for the general public too. I'm completely without clue when it
comes to marketing to Mr. Pooblic - especially over a broad geographic
area (better than half of a state). About all I can come up with is to
publish my toll-free number in a few yellow pages books across the
southern half of the state and hope for the best.

So, I Haven't a clue what this may cost, or even how to go about getting
a quote. Can you even do this without a local number in each target
city? Will the cost make me want to cry? And does anyone have any
better ideas for marketing Investigative work over a broad area?

Thanks for any reply you can offer.
Bryan