Pocket doors in a bearing wall require a wall depth that is significantly greater than standard 2x4 construction. I have a 102 year old house with pocket doors between the living and dining rooms, and the wall depth is almost 1 foot (it is also a bearing wall). Basically, it's a 2x4 wall on each side of the pocket door opening. You also must have enough wall length on each side of the door opening to fully accomodate the width of the door that is sliding into it. If you are still game to do this, you can buy the pocket door apparatus at most home centers, and the instructions are easy to follow. Simply use your current wall for one side of the pocket, leave the door gap, and build another 2x4 wall for the second side of the pocket. Plan to completely re-face the wood trim around the door opening. Good luck!