LT,
I am south of you in San Antonio. just clean up the break as best as you can. Once the cleaned up break dries out you can seal it with pruning tar or Dap caulk. If you can leave a few inches of branch there's a good chance it will regrow from the branch. if you cut it flush with the joint then it will never regrow from the joint.

A 15 year old plant should be just fine to prune at any time. I like to prune in March mostly because its the easiest time to root the cut branches.

The first thing to do with the broken branch is remove all of the leaves, then clean the break and dip it in rooting hormone. you can let it air dry or use a humidity chamber for about 2 weeks. At that point you could start the rooting process. I like using perlite or a mix of perlite and soil 3 to1 and bottom heat from a heat mat. Chances are pretty good with branch of that size it will root for you. Good luck with it.