In Houston the probate courts don't use 'pattern forms' so you'll need to contact someone locally to help you through this. My recommendation is to contact the South Texas College of Law legal clinic in downtown Houston and ask them if they can provide you with some assistance. The University of Houston and Texas Southern University Law School may also have legal clinic programs that can assist you. You may also contact the Harris County Clerk's Office for additional information about the Civil District Probate Courts located downtown.
There really is not substitute for getting this right. So, I have to recommend that you get good probate counsel from the start!