I'm surprised they are pushing you to get the sleeve with your history of gerd. It would make me wonder if they're more confident in preforming the sleeve rather than RNY. You might want to get a second opinion.
Ice! You can freeze Water in a Dixie cup & then use the big ice cube to massage your hip.
I have also used a “muscle roller stick” on my hip when it felt like a very, very tight muscle in my hip.
A foam roller can also help.