You may be able to find a selectable diverter to a hand shower unit and install the hand mount to the wall for use as a showerhead. This would allow you to use both the bath and shower.
The deck mount garden tub faucets won't have a diverter feature. You could leave that faucet in place and "T" off the plumbing to go to a standard shower faucet plumbing.
The shower wall could be a problem too. If the depth of the garden tub is over 36", it will be real hard to find a reasonable priced wall kit. Most 60" wide wall kits are made to fit 30"-32" tubs. You could call the seamless shower wall people, they could fix you up pretty nice. You could also use flat wall panels, like the Thrifty Tile Board panels from Lowe's or other home stores. Of course for a zillion dollars and 82 cents you can go with Swanstone or Corian.
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All information and advice given is for entertainment and informational purposes only. The person doing the work is solely responsible to insure that their work complies with their local building code and OSHA safety regulations.