This depends on many factors, like the types of fixtures you want and the labor you acquire. There's a safe range we can tell you where your final bill will lie. You can expect the cost to be between $800 to $12000. Since you're adding a shower, you'll need at least three fixtures and their points to be accommodated in the wall. You'll also require an additional space of 5x7 feet in your bathroom. If this is difficult to obtain, the cost will increase and requires you to change your plumbing and tiles.