The one piece shower is made for new construction, since in most cases getting one through a 24" bathroom door might be impossible. I would recommend a three piece shower surround that can be sealed with 100% silicone caulk with mold resistant compounds. A decent brand carried by Home Depo or Lowe's will run around $400.00 (dollars), with three walls and a pan base. The draw back with acrylic or fiberglass surrounds is that you can't use lie soap or abrasive cleaning methods otherwise the sheen will turn dull in a very short period. As for your difficulty with tile and grout maintenance, a good weekly cleaning with a strong solution of bleach water will prevent scum and mold buildup, while not effecting the hard surface of ceramic or porcelain tile.