It depends on who will do the design work (thinking through portion... what materials, shape, height, size, pitch, details, etc.) If you, call a paver subcontractor. Here (Florida) we have paver subs who advertise regularly in local papers and some of them also advertise on craigslist. If a landscape designer, start there and find someone capable of designing hardscape. If you call a landscape contractor who does hardscape work or a hardscape contractor, they will have designers on staff who can help you. They will design and build it.

Go to one of your local garden centers, not HD or Lowe's. if you have a recommendation from someone, all the better. Not only can you purchase plantings, but if they don't have hardscape materials, most will have the availability to get it, and have an installer. It worked for me. ;o)

If you want the same exact materials in the same exact layout you could call a landscape construction company or a masonry company and they can demo and rebuild what you have.

If you want to alter the design from the original you will have to find a firm that is billed as design + build Or hire an independent designer who will come up with a new design and will send out the plans to several bidding contractors for competitive pricing.

You might want to call your planning and building department to see if a permit is required or when you interview the various building companies who have a proven portfolio of work similar to your required needs, they will let you know if you require a permit or not.

In my area of the country if your walls are a certain height above grade you will require a structual engineer to calculate and design the retainment walls.

If you know that your area will require a structural engineer to calc. the walls then it is cost effective to hire an engineering landscape construction company . They'll calc. the walls, draw up the spec's, submit for permit and build the project.

Oh cr*p this sounds like a lot of money....

I'm hoping to move in a few years and don't need anything jaw-droppingly gorgeous and don't want to spend an exorbitant amount of money, if I could just get someone to re-do pretty much the way it is (square) in brick or stone I'd be happy.

Thank you so much for your input - really good info and I really appreciate it, this is all new to me (not the landscaping but the walls) :0)

I suggest you post a photo that clearly explains what you're dealing with and you might get "tighter" advice. After reading again, I'm not exactly sure what part is caving in. I thought it was the deck part. A photo will help.