Legal Question in Family Law in Texas

I'm not sure quite what you mean about the whole nine yards, but as far as changing your name goes, no you definitely do not have to do that (ever, actually). In fact, your name stays the same by default, so all you have to do to keep it the same is...nothing. About getting married in general, assuming you're both 18, competent, not married to anyone else and all that, all you have to do is go down to your county courthouse and fill out a marriage license application with the county clerk (basically confirming all those issues above plus a couple more). The clerk will then issue your license, and 72 hours later, you'll be able to get married--no name change, frilly white dress, or mother of the bride required. I think the license may only be valid for thirty days, though, so don't get it until you're ready to get married.