Here's one good resource:
http://www.parktool.com/repair_help/FAQindex.shtml Click on the "Bike Map" and you're on your way
A good mechanic can probably fix your existing wheel if all that's the matter is that it's got some broken spokes, but in my opinion, if the stock rear wheel has begun to break spokes, then the stock spokes have probably reached the end of their fatigue life, and the problem will happen again. So if you're in doubt whether to repair or replace, I vote for "replace."