Most referral services are pretty useless, basically it's just the dentist paying for the pleasure and passing the cost onto the customer. The "screening" consists of nothing more than checking that the dentist has a valid license... and you can just as easily do that yourself by going to your state dental board's website...
Regarding dental discount plans - stay away from them if you can at all afford to. They may make sense under some circumstances, but a lot of the time they don't.
In order to make up for losses incurred by the discount plan, the dentist is forced to make up for it either by taking on a huge volume of patients (and it's difficult to get the time you'll want and need to overcome your fears), or by selling you unnecessary (optional or over-the-top) procedures. There may be some dentists around who accept these plans out of the goodness of their hearts, but this would be quite rare.
I'd say most dentists would rather not participate in these schemes, but in very competitive areas of the country, they're sometimes the only choice for someone without an established customer base.
Personally, I wouldn't recommend choosing a dentist on the basis that they accept a discount plan.
As Mirla said, asking for recommendations can be daunting - but it really is the best way to find a dentist that people like and are happy with. Do you know anyone who could ask around for you?