What resources can you recommend for designing a garden to replace an existing garden that had many "failed" and overgrown plants?
Answer
Contact a Landscape Designer or Landscape Architect. There are many factors involved in landscape design such as, site analysis to determine the sun/shade, wind, etc. information, the soil quality, drainage, ultimate size of plant material, etc.. You can have an initial consultation which may be enough, but it sounds like you need a finished plan if you have had many failures.