Peaches and nectarines are usually pruned during the winter dormant season. It's important to know that fruiting takes place on one year old wood.
The UC Integrated Pest Management website has a brief summary of peach and nectarine tree pruning.
Even if you hire someone for the job, it is good to know a bit about the proper way to prune your trees. For the basics of fruit tree pruning you may be interested in viewing our video on fruit tree pruning
. However, for specific instructions for pruning peach trees, there are several videos on Youtube:
We can't make specific recommendations for people for your job. We can refer you to a way to find a certified arborist
. You may want to consult Yelp or other online resources to see what others thought of their work.