The first thing I would do is to start here:
http://www.akc.org/breeds/parson_russell_terrier/index.cfm
This will give you an idea if your bitch is up to standard.
Personally I would not breed any bitch until at least 2.5 yrs old. That's just me though, I do know some breeders that will finish their dogs and put them into the breeding program at 1.5-2 yrs of age. That's too early in my estimation.
The ACA is not a preferred registry with hobby breeders. The reason for this is that registering with the ACA does not even require a pedigree. Heck, according to their
site you don't even have to provide breed information.
The ACA does have events. http://www.acacanines.com/ACA%20Website%202007/dogshows.html"]
However it doesn't appear that they are too interested in conformation events at all. The health certifications that the registry offers are, for the most part, a joke.
I tend to agree with Hounded and the majority of the others on this thread so far. You would better serve the breed and yourself by becoming involved in the breed, finding a mentor and spaying the bitch you have now. When it's tme for a new pup, purchase one from show lines, as a conformation dog, and prove her in the show ring and in performance events. That's when you'll truly know what you have.
One of the biggest beefs I have with breeders is that most breeders do not make provision for taking back ALL of the dogs that they've bred. A breeder is responsible for those pups for life. One of my friends was expecting a litter and had 4 adult dogs returned to her for various reasons-the last arriving less than a week before the pups were whelped. She ended up having 17 or 18 dogs in her house for 12 weeks or so.
So be prepared to take back any pups you adopt at any time of their lives-without question.
I don't mean to sound cold or off putting, I'm just very pragmatic when it comes to puppies and dogs. Each of us in our respective breeds tends to be that way though some, like me, are super protective of our breed. Even though I love my breed and they are perfect for me, (as I'm sure you feel about your terrier) I can tell you that these dogs aren't perfect for many people.
Sorry to be so long winded.