I have found that not all states have the same levels of "extension agency assistance" so I agree with you on your assessment that much of what you find is targeting ranchers.
There are soil testing kits that are available for people to test their own soil samples (check seed catalogs or online sources if you can't find one locally). These are pretty simple (they use color matching for most tests) and get the basic information. You definitely need to test the pH of your soil. Compost is always a good idea for Texas (or anywhere else) because nutrients are used up as gardens grow. We mulch the heck out of our gardens (hay straw used to be cheap but not this year). The great thing about mulch is you work it into the soil after the growing season and it breaks down (slow composting).
Cold crops are great. Don't forget herbs (mine grow year round usually). You might have good luck with square foot gardening or "hills" rather than rows. The plants shade each other's roots and along with the mulch reduce the need for extra watering. Good luck.