Re: Second opinion
From fifty years of experience I would say if your master cylinder is bad the wheel cylinders will be next to go. this is due to the fact that brake fluid absorbs water. Water and aluminum pistons in a cast iron bore is a recipe for failure.
Rebuilt wheel cylinders are cheap. You need to flush the lines to get rid of the old fluid. So why not bite the bullet and do a full break job at the same time (don't have to change the shoes unless they have brake fluid on them or they are worn out).