I think whatever you use to replace the timbers will cost about the same.... unless there's plenty of big rocks where you live? I'm sure you're going to want to keep some kind of retaining wall in the back to prevent soil erosion down that slope? But for the front, it would probably be a big undertaking to level out the entire area. But you could try sloping it. Palustris had a very detailed posting of a similar area he called "a crevice garden". Let me see if I can find it. here ya go: http://www.gardenstew.com/viewtopic.php?t=24305&highlight= Maybe you can do something like that?